id
stringlengths 9
16
| submitter
stringlengths 1
64
⌀ | authors
stringlengths 3
7.28k
| title
stringlengths 3
382
| comments
stringlengths 1
915
⌀ | journal-ref
stringlengths 4
386
⌀ | doi
stringlengths 9
129
⌀ | report-no
stringlengths 1
341
⌀ | categories
stringclasses 5
values | license
stringclasses 9
values | abstract
stringlengths 20
2.75k
| update_date
stringlengths 10
10
|
|---|---|---|---|---|---|---|---|---|---|---|---|
0704.0001 | Pavel Nadolsky | C. Bal\'azs, E. L. Berger, P. M. Nadolsky, C.-P. Yuan | Calculation of prompt diphoton production cross sections at Tevatron and
LHC energies | 37 pages, 15 figures; published version | Phys.Rev.D76:013009,2007 | 10.1103/PhysRevD.76.013009 | ANL-HEP-PR-07-12 | hep-ph | null | A fully differential calculation in perturbative quantum chromodynamics is
presented for the production of massive photon pairs at hadron colliders. All
next-to-leading order perturbative contributions from quark-antiquark,
gluon-(anti)quark, and gluon-gluon subprocesses are included, as well as
all-orders resummation of initial-state gluon radiation valid at
next-to-next-to-leading logarithmic accuracy. The region of phase space is
specified in which the calculation is most reliable. Good agreement is
demonstrated with data from the Fermilab Tevatron, and predictions are made for
more detailed tests with CDF and DO data. Predictions are shown for
distributions of diphoton pairs produced at the energy of the Large Hadron
Collider (LHC). Distributions of the diphoton pairs from the decay of a Higgs
boson are contrasted with those produced from QCD processes at the LHC, showing
that enhanced sensitivity to the signal can be obtained with judicious
selection of events.
| 2008-11-26 |
0704.0009 | Paul Harvey | Paul Harvey, Bruno Merin, Tracy L. Huard, Luisa M. Rebull, Nicholas
Chapman, Neal J. Evans II, Philip C. Myers | The Spitzer c2d Survey of Large, Nearby, Insterstellar Clouds. IX. The
Serpens YSO Population As Observed With IRAC and MIPS | null | Astrophys.J.663:1149-1173,2007 | 10.1086/518646 | null | astro-ph | null | We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy
observations of the Serpens star-forming region. In particular we present a set
of criteria for isolating bona fide young stellar objects, YSO's, from the
extensive background contamination by extra-galactic objects. We then discuss
the properties of the resulting high confidence set of YSO's. We find 235 such
objects in the 0.85 deg^2 field that was covered with both IRAC and MIPS. An
additional set of 51 lower confidence YSO's outside this area is identified
from the MIPS data combined with 2MASS photometry. We describe two sets of
results, color-color diagrams to compare our observed source properties with
those of theoretical models for star/disk/envelope systems and our own modeling
of the subset of our objects that appear to be star+disks. These objects
exhibit a very wide range of disk properties, from many that can be fit with
actively accreting disks to some with both passive disks and even possibly
debris disks. We find that the luminosity function of YSO's in Serpens extends
down to at least a few x .001 Lsun or lower for an assumed distance of 260 pc.
The lower limit may be set by our inability to distinguish YSO's from
extra-galactic sources more than by the lack of YSO's at very low luminosities.
A spatial clustering analysis shows that the nominally less-evolved YSO's are
more highly clustered than the later stages and that the background
extra-galactic population can be fit by the same two-point correlation function
as seen in other extra-galactic studies. We also present a table of matches
between several previous infrared and X-ray studies of the Serpens YSO
population and our Spitzer data set.
| 2010-03-18 |
0704.0015 | Christian Stahn | Christian Stahn | Fermionic superstring loop amplitudes in the pure spinor formalism | 22 pages; signs and coefficients adjusted for anticommuting
superfields, section 4.3 changed accordingly, reference added | JHEP 0705:034,2007 | 10.1088/1126-6708/2007/05/034 | null | hep-th | null | The pure spinor formulation of the ten-dimensional superstring leads to
manifestly supersymmetric loop amplitudes, expressed as integrals in pure
spinor superspace. This paper explores different methods to evaluate these
integrals and then uses them to calculate the kinematic factors of the one-loop
and two-loop massless four-point amplitudes involving two and four Ramond
states.
| 2009-11-13 |
0704.0016 | Li Tong | Chao-Hsi Chang, Tong Li, Xue-Qian Li and Yu-Ming Wang | Lifetime of doubly charmed baryons | 17 pages, 3 figures and 1 table | Commun.Theor.Phys.49:993-1000,2008 | 10.1088/0253-6102/49/4/38 | null | hep-ph | null | In this work, we evaluate the lifetimes of the doubly charmed baryons
$\Xi_{cc}^{+}$, $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. We carefully calculate
the non-spectator contributions at the quark level where the Cabibbo-suppressed
diagrams are also included. The hadronic matrix elements are evaluated in the
simple non-relativistic harmonic oscillator model. Our numerical results are
generally consistent with that obtained by other authors who used the diquark
model. However, all the theoretical predictions on the lifetimes are one order
larger than the upper limit set by the recent SELEX measurement. This
discrepancy would be clarified by the future experiment, if more accurate
experiment still confirms the value of the SELEX collaboration, there must be
some unknown mechanism to be explored.
| 2008-12-18 |
0704.0017 | Nceba Mhlahlo | Nceba Mhlahlo, David H. Buckley, Vikram S. Dhillon, Steven B. Potter,
Brian Warner and Patric A. Woudt | Spectroscopic Observations of the Intermediate Polar EX Hydrae in
Quiescence | 10 pages, 11 figures (figures 3, 4, 7 and 8 at reduced resolution,
originals available on request). Accepted for publication in Monthly Notices
of the Royal Astronomical Society | Mon.Not.Roy.Astron.Soc.378:211-220,2007 | 10.1111/j.1365-2966.2007.11762.x | null | astro-ph | null | Results from spectroscopic observations of the Intermediate Polar (IP) EX Hya
in quiescence during 1991 and 2001 are presented. Spin-modulated radial
velocities consistent with an outer disc origin were detected for the first
time in an IP. The spin pulsation was modulated with velocities near ~500-600
km/s. These velocities are consistent with those of material circulating at the
outer edge of the accretion disc, suggesting corotation of the accretion
curtain with material near the Roche lobe radius. Furthermore, spin Doppler
tomograms have revealed evidence of the accretion curtain emission extending
from velocities of ~500 km/s to ~1000 km/s. These findings have confirmed the
theoretical model predictions of King & Wynn (1999), Belle et al. (2002) and
Norton et al. (2004) for EX Hya, which predict large accretion curtains that
extend to a distance close to the Roche lobe radius in this system. Evidence
for overflow stream of material falling onto the magnetosphere was observed,
confirming the result of Belle et al. (2005) that disc overflow in EX Hya is
present during quiescence as well as outburst. It appears that the hbeta and
hgamma spin radial velocities originated from the rotation of the funnel at the
outer disc edge, while those of halpha were produced due to the flow of
material along the field lines far from the white dwarf (narrow component) and
close to the white dwarf (broad-base component), in agreement with the
accretion curtain model.
| 2009-06-23 |
0704.0018 | Andreas Gustavsson | Andreas Gustavsson | In quest of a generalized Callias index theorem | 20 pages, v2: an overall sign and typos corrected | null | null | null | hep-th | null | We give a prescription for how to compute the Callias index, using as
regulator an exponential function. We find agreement with old results in all
odd dimensions. We show that the problem of computing the dimension of the
moduli space of self-dual strings can be formulated as an index problem in
even-dimensional (loop-)space. We think that the regulator used in this Letter
can be applied to this index problem.
| 2007-05-23 |
0704.0023 | Maria Loukitcheva | M. A. Loukitcheva, S. K. Solanki and S. White | ALMA as the ideal probe of the solar chromosphere | 4 pages, 2 figures, to appear in the proceedings of the conference
Science with ALMA: a new era for Astrophysics, Spain, 2006 | Astrophys.Space Sci.313:197-200,2008 | 10.1007/s10509-007-9626-1 | null | astro-ph | null | The very nature of the solar chromosphere, its structuring and dynamics,
remains far from being properly understood, in spite of intensive research.
Here we point out the potential of chromospheric observations at millimeter
wavelengths to resolve this long-standing problem. Computations carried out
with a sophisticated dynamic model of the solar chromosphere due to Carlsson
and Stein demonstrate that millimeter emission is extremely sensitive to
dynamic processes in the chromosphere and the appropriate wavelengths to look
for dynamic signatures are in the range 0.8-5.0 mm. The model also suggests
that high resolution observations at mm wavelengths, as will be provided by
ALMA, will have the unique property of reacting to both the hot and the cool
gas, and thus will have the potential of distinguishing between rival models of
the solar atmosphere. Thus, initial results obtained from the observations of
the quiet Sun at 3.5 mm with the BIMA array (resolution of 12 arcsec) reveal
significant oscillations with amplitudes of 50-150 K and frequencies of 1.5-8
mHz with a tendency toward short-period oscillations in internetwork and longer
periods in network regions. However higher spatial resolution, such as that
provided by ALMA, is required for a clean separation between the features
within the solar atmosphere and for an adequate comparison with the output of
the comprehensive dynamic simulations.
| 2009-06-23 |
0704.0029 | Weizhen Deng | Zhan Shu, Xiao-Lin Chen and Wei-Zhen Deng | Understanding the Flavor Symmetry Breaking and Nucleon Flavor-Spin
Structure within Chiral Quark Model | null | Phys.Rev.D75:094018,2007 | 10.1103/PhysRevD.75.094018 | null | hep-ph | null | In $\XQM$, a quark can emit Goldstone bosons. The flavor symmetry breaking in
the Goldstone boson emission process is used to intepret the nucleon
flavor-spin structure. In this paper, we study the inner structure of
constituent quarks implied in $\XQM$ caused by the Goldstone boson emission
process in nucleon. From a simplified model Hamiltonian derived from $\XQM$,
the intrinsic wave functions of constituent quarks are determined. Then the
obtained transition probabilities of the emission of Goldstone boson from a
quark can give a reasonable interpretation to the flavor symmetry breaking in
nucleon flavor-spin structure.
| 2010-04-23 |
0704.0031 | Valery M. Biryukov | V. M. Biryukov (Serpukhov, IHEP) | Crystal channeling of LHC forward protons with preserved distribution in
phase space | 11 pages, 3 figures | Phys.Lett.B658:7-12,2007 | 10.1016/j.physletb.2007.10.051 | null | hep-ph | null | We show that crystal can trap a broad (x, x', y, y', E) distribution of
particles and channel it preserved with a high precision. This sampled-and-hold
distribution can be steered by a bent crystal for analysis downstream. In
simulations for the 7 TeV Large Hadron Collider, a crystal adapted to the
accelerator lattice traps 90% of diffractively scattered protons emerging from
the interaction point with a divergence 100 times the critical angle. We set
the criterion for crystal adaptation improving efficiency ~100-fold. Proton
angles are preserved in crystal transmission with accuracy down to 0.1
microrad. This makes feasible a crystal application for measuring very forward
protons at the LHC.
| 2008-11-26 |
0704.0032 | Andreu Esteban-Pretel | A. Esteban-Pretel, R. Tom\`as and J. W. F. Valle | Probing non-standard neutrino interactions with supernova neutrinos | 21 pages, 12 figures, 17 postscript files | Phys.Rev.D76:053001,2007 | 10.1103/PhysRevD.76.053001 | null | hep-ph | null | We analyze the possibility of probing non-standard neutrino interactions
(NSI, for short) through the detection of neutrinos produced in a future
galactic supernova (SN).We consider the effect of NSI on the neutrino
propagation through the SN envelope within a three-neutrino framework, paying
special attention to the inclusion of NSI-induced resonant conversions, which
may take place in the most deleptonised inner layers. We study the possibility
of detecting NSI effects in a Megaton water Cherenkov detector, either through
modulation effects in the $\bar\nu_e$ spectrum due to (i) the passage of shock
waves through the SN envelope, (ii) the time dependence of the electron
fraction and (iii) the Earth matter effects; or, finally, through the possible
detectability of the neutronization $\nu_e$ burst. We find that the $\bar\nu_e$
spectrum can exhibit dramatic features due to the internal NSI-induced resonant
conversion. This occurs for non-universal NSI strengths of a few %, and for
very small flavor-changing NSI above a few$\times 10^{-5}$.
| 2008-11-26 |
0704.0052 | William Gordon Ritter | Arthur Jaffe (1) and Gordon Ritter (1) ((1) Harvard University) | Quantum Field Theory on Curved Backgrounds. II. Spacetime Symmetries | 18 pages, 1 figure | null | null | null | hep-th | null | We study space-time symmetries in scalar quantum field theory (including
interacting theories) on static space-times. We first consider Euclidean
quantum field theory on a static Riemannian manifold, and show that the
isometry group is generated by one-parameter subgroups which have either
self-adjoint or unitary quantizations. We analytically continue the
self-adjoint semigroups to one-parameter unitary groups, and thus construct a
unitary representation of the isometry group of the associated Lorentzian
manifold. The method is illustrated for the example of hyperbolic space, whose
Lorentzian continuation is Anti-de Sitter space.
| 2007-05-23 |
0704.0059 | Thomas Beatty | T. G. Beatty, J. M. Fernandez, D. W. Latham, G. A. Bakos, G. Kovacs,
R. W. Noyes, R. P. Stefanik, G. Torres, M. E. Everett, C. W. Hergenrother | The Mass and Radius of the Unseen M-Dwarf Companion in the Single-Lined
Eclipsing Binary HAT-TR-205-013 | 18 pages, 9 tables and 6 figures; accepted by ApJ. Added a reference
and corrected a typo | Astrophys.J.663:573-582,2007 | 10.1086/518413 | null | astro-ph | null | We derive masses and radii for both components in the single-lined eclipsing
binary HAT-TR-205-013, which consists of a F7V primary and a late M-dwarf
secondary. The system's period is short, $P=2.230736 \pm 0.000010$ days, with
an orbit indistinguishable from circular, $e=0.012 \pm 0.021$. We demonstrate
generally that the surface gravity of the secondary star in a single-lined
binary undergoing total eclipses can be derived from characteristics of the
light curve and spectroscopic orbit. This constrains the secondary to a unique
line in the mass-radius diagram with $M/R^2$ = constant. For HAT-TR-205-013, we
assume the orbit has been tidally circularized, and that the primary's rotation
has been synchronized and aligned with the orbital axis. Our observed line
broadening, $V_{\rm rot} \sin i_{\rm rot} = 28.9 \pm 1.0$ \kms, gives a primary
radius of $R_{\rm A} = 1.28 \pm 0.04$ \rsun. Our light curve analysis leads to
the radius of the secondary, $R_{\rm B} = 0.167 \pm 0.006$ \rsun, and the
semimajor axis of the orbit, $a = 7.54 \pm 0.30 \rsun = 0.0351 \pm 0.0014$ AU.
Our single-lined spectroscopic orbit and the semimajor axis then yield the
individual masses, $M_{\rm B} = 0.124 \pm 0.010$ \msun and $M_{\rm A} = 1.04
\pm 0.13$ \msun. Our result for HAT-TR-205-013 B lies above the theoretical
mass-radius models from the Lyon group, consistent with results from
double-lined eclipsing binaries. The method we describe offers the opportunity
to study the very low end of the stellar mass-radius relation.
| 2009-06-23 |
0704.0063 | Somnath Choudhury | Somnath Choudhury | Experimental efforts in search of 76Ge Neutrinoless Double Beta Decay | null | null | null | null | hep-ph | null | Neutrinoless double beta decay is one of the most sensitive approaches in
non-accelerator particle physics to take us into a regime of physics beyond the
standard model. This article is a brief review of the experiments in search of
neutrinoless double beta decay from 76Ge. Following a brief introduction of the
process of double beta decay from 76Ge, the results of the very first
experiments IGEX and Heidelberg-Moscow which give indications of the existence
of possible neutrinoless double beta decay mode has been reviewed. Then ongoing
efforts to substantiate the early findings are presented and the Majorana
experiment as a future experimental approach which will allow a very detailed
study of the neutrinoless decay mode is discussed.
| 2008-03-12 |
0704.0064 | Rudra Prakash Malik | R. P. Malik (Bhu) | Nilpotent symmetry invariance in the superfield formulation: the
(non-)Abelian 1-form gauge theories | LaTeX file, 19 pages, journal reference | Int.J.Mod.Phys.A23:3685-3705,2008 | 10.1142/S0217751X08041591 | null | hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We capture the off-shell as well as the on-shell nilpotent
Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetry invariance of the
Lagrangian densities of the four (3 + 1)-dimensional (4D) (non-)Abelian 1-form
gauge theories within the framework of the superfield formalism. In particular,
we provide the geometrical interpretations for (i) the above nilpotent symmetry
invariance, and (ii) the above Lagrangian densities, in the language of the
specific quantities defined in the domain of the above superfield formalism.
Some of the subtle points, connected with the 4D (non-)Abelian 1-form gauge
theories, are clarified within the framework of the above superfield formalism
where the 4D ordinary gauge theories are considered on the (4, 2)-dimensional
supermanifold parametrized by the four spacetime coordinates x^\mu (with \mu =
0, 1, 2, 3) and a pair of Grassmannian variables \theta and \bar\theta. One of
the key results of our present investigation is a great deal of simplification
in the geometrical understanding of the nilpotent (anti-)BRST symmetry
invariance.
| 2008-11-26 |
0704.0066 | Bozhidar Zakhariev Iliev | Bozhidar Z. Iliev (Institute for Nuclear Research and Nuclear Energy,
Bulgarian Academy of Sciences, Sofia, Bulgaria) | Lagrangian quantum field theory in momentum picture. IV. Commutation
relations for free fields | 60 LaTeX pages. The packages AMS-LaTeX and amsfonts are required.
This paper is a continuation of the e-print E-prints No. hep-th/0402006, No.
hep-th/0405008 and No. hep-th/0505007. For related papers, visit the
"publication" pages at http://theo.inrne.bas.bg/~bozho/ | null | null | null | hep-th | null | Possible (algebraic) commutation relations in the Lagrangian quantum theory
of free (scalar, spinor and vector) fields are considered from mathematical
view-point. As sources of these relations are employed the Heisenberg
equations/relations for the dynamical variables and a specific condition for
uniqueness of the operators of the dynamical variables (with respect to some
class of Lagrangians). The paracommutation relations or some their
generalizations are pointed as the most general ones that entail the validity
of all Heisenberg equations. The simultaneous fulfillment of the Heisenberg
equations and the uniqueness requirement turn to be impossible. This problem is
solved via a redefinition of the dynamical variables, similar to the normal
ordering procedure and containing it as a special case. That implies
corresponding changes in the admissible commutation relations. The introduction
of the concept of the vacuum makes narrow the class of the possible commutation
relations; in particular, the mentioned redefinition of the dynamical variables
is reduced to normal ordering. As a last restriction on that class is imposed
the requirement for existing of an effective procedure for calculating vacuum
mean values. The standard bilinear commutation relations are pointed as the
only known ones that satisfy all of the mentioned conditions and do not
contradict to the existing data.
| 2007-05-23 |
0704.0080 | Dean McLaughlin | Dean E. McLaughlin and S. Michael Fall | Shaping the Globular Cluster Mass Function by Stellar-Dynamical
Evaporation | Final version, matching the published paper | Astrophys.J.679:1272-1287,2008 | 10.1086/533485 | null | astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the globular cluster mass function (GCMF) in the Milky Way
depends on cluster half-mass density (rho_h) in the sense that the turnover
mass M_TO increases with rho_h while the width of the GCMF decreases. We argue
that this is the expected signature of the slow erosion of a mass function that
initially rose towards low masses, predominantly through cluster evaporation
driven by internal two-body relaxation. We find excellent agreement between the
observed GCMF -- including its dependence on internal density rho_h, central
concentration c, and Galactocentric distance r_gc -- and a simple model in
which the relaxation-driven mass-loss rates of clusters are approximated by
-dM/dt = mu_ev ~ rho_h^{1/2}. In particular, we recover the well-known
insensitivity of M_TO to r_gc. This feature does not derive from a literal
``universality'' of the GCMF turnover mass, but rather from a significant
variation of M_TO with rho_h -- the expected outcome of relaxation-driven
cluster disruption -- plus significant scatter in rho_h as a function of r_gc.
Our conclusions are the same if the evaporation rates are assumed to depend
instead on the mean volume or surface densities of clusters inside their tidal
radii, as mu_ev ~ rho_t^{1/2} or mu_ev ~ Sigma_t^{3/4} -- alternative
prescriptions that are physically motivated but involve cluster properties
(rho_t and Sigma_t) that are not as well defined or as readily observable as
rho_h. In all cases, the normalization of mu_ev required to fit the GCMF
implies cluster lifetimes that are within the range of standard values
(although falling towards the low end of this range). Our analysis does not
depend on any assumptions or information about velocity anisotropy in the
globular cluster system.
| 2010-11-11 |
0704.0083 | Andrei Barvinsky | A.O.Barvinsky | Why there is something rather than nothing (out of everything)? | 4 pages, RevTex, several references added and minor changes done | Phys.Rev.Lett.99:071301,2007 | 10.1103/PhysRevLett.99.071301 | null | hep-th | null | The path integral over Euclidean geometries for the recently suggested
density matrix of the Universe is shown to describe a microcanonical ensemble
in quantum cosmology. This ensemble corresponds to a uniform (weight one)
distribution in phase space of true physical variables, but in terms of the
observable spacetime geometry it is peaked about complex saddle-points of the
{\em Lorentzian} path integral. They are represented by the recently obtained
cosmological instantons limited to a bounded range of the cosmological
constant. Inflationary cosmologies generated by these instantons at late stages
of expansion undergo acceleration whose low-energy scale can be attained within
the concept of dynamically evolving extra dimensions. Thus, together with the
bounded range of the early cosmological constant, this cosmological ensemble
suggests the mechanism of constraining the landscape of string vacua and,
simultaneously, a possible solution to the dark energy problem in the form of
the quasi-equilibrium decay of the microcanonical state of the Universe.
| 2008-11-26 |
0704.0085 | Partha Mukhopadhyay | Partha Mukhopadhyay | A Universality in PP-Waves | LaTeX file, 43 pages, one reference added, minor changes made | JHEP 0706:061,2007 | 10.1088/1126-6708/2007/06/061 | DAMTP-2007-30 | hep-th | null | We discuss a universality property of any covariant field theory in
space-time expanded around pp-wave backgrounds. According to this property the
space-time lagrangian density evaluated on a restricted set of field
configurations, called universal sector, turns out to be same around all the
pp-waves, even off-shell, with same transverse space and same profiles for the
background scalars. In this paper we restrict our discussion to tensorial
fields only. In the context of bosonic string theory we consider on-shell
pp-waves and argue that universality requires the existence of a universal
sector of world-sheet operators whose correlation functions are insensitive to
the pp-wave nature of the metric and the background gauge flux. Such results
can also be reproduced using the world-sheet conformal field theory. We also
study such pp-waves in non-polynomial closed string field theory (CSFT). In
particular, we argue that for an off-shell pp-wave ansatz with flat transverse
space and dilaton independent of transverse coordinates the field redefinition
relating the low energy effective field theory and CSFT with all the massive
modes integrated out is at most quadratic in fields. Because of this
simplification it is expected that the off-shell pp-waves can be identified on
the two sides. Furthermore, given the massless pp-wave field configurations, an
iterative method for computing the higher massive modes using the CSFT
equations of motion has been discussed. All our bosonic string theory analyses
can be generalised to the common Neveu-Schwarz sector of superstrings.
| 2009-11-13 |
0704.0094 | HongSheng Zhao | HongSheng Zhao (SUPA, St Andrews) | Timing and Lensing of the Colliding Bullet Clusters: barely enough time
and gravity to accelerate the bullet | 5-pages, Physical Review D, rapid publication submitted | null | null | null | astro-ph | null | We present semi-analytical constraint on the amount of dark matter in the
merging bullet galaxy cluster using the classical Local Group timing arguments.
We consider particle orbits in potential models which fit the lensing data.
{\it Marginally consistent} CDM models in Newtonian gravity are found with a
total mass M_{CDM} = 1 x 10^{15}Msun of Cold DM: the bullet subhalo can move
with V_{DM}=3000km/s, and the "bullet" X-ray gas can move with
V_{gas}=4200km/s. These are nearly the {\it maximum speeds} that are
accelerable by the gravity of two truncated CDM halos in a Hubble time even
without the ram pressure. Consistency breaks down if one adopts higher end of
the error bars for the bullet gas speed (5000-5400km/s), and the bullet gas
would not be bound by the sub-cluster halo for the Hubble time. Models with
V_{DM}~ 4500km/s ~ V_{gas} would invoke unrealistic large amount M_{CDM}=7x
10^{15}Msun of CDM for a cluster containing only ~ 10^{14}Msun of gas. Our
results are generalisable beyond General Relativity, e.g., a speed of
$4500\kms$ is easily obtained in the relativistic MONDian lensing model of
Angus et al. (2007). However, MONDian model with little hot dark matter
$M_{HDM} \le 0.6\times 10^{15}\msun$ and CDM model with a small halo mass $\le
1\times 10^{15}\msun$ are barely consistent with lensing and velocity data.
| 2007-05-23 |
0704.0101 | Paolo Di Vecchia pdv | Paolo Di Vecchia | The birth of string theory | Latex 60 pages, 2 figures, uses svmult.cls. Contribution to the
volume "String theory and fundamental interactions", dedicated to Gabriele
Veneziano on his 65th birthday. | Lect.NotesPhys.737:59-118,2008 | null | NORDITA-2007-13 | hep-th | null | In this contribution we go through the developments that in the years 1968 to
1974 led from the Veneziano model to the bosonic string.
| 2008-11-26 |
0704.0117 | Mang Feng | T. Liu, K.L. Wang, and M. Feng | Lower ground state due to counter-rotating wave interaction in trapped
ion system | Complete solution of a trapped ion in both strong and weak excitation
regimes and beyond Lamb-Dicke limit. Also applicable to JC model relevant
problems | null | 10.1088/0953-4075/40/11/002 | null | quant-ph | null | We consider a single ion confined in a trap under radiation of two traveling
waves of lasers. In the strong-excitation regime and without the restriction of
Lamb-Dicke limit, the Hamiltonian of the system is similar to a driving
Jaynes-Cummings model without rotating wave approximation (RWA). The approach
we developed enables us to present a complete eigensolutions, which makes it
available to compare with the solutions under the RWA. We find that, the ground
state in our non-RWA solution is energically lower than the counterpart under
the RWA. If we have the ion in the ground state, it is equivalent to a spin
dependent force on the trapped ion. Discussion is made for the difference
between the solutions with and without the RWA, and for the relevant
experimental test, as well as for the possible application in quantum
information processing.
| 2009-11-13 |
0704.0121 | Changhyun Ahn | Changhyun Ahn | Meta-Stable Brane Configuration of Product Gauge Groups | 27 pp; 7 figures; Pages 8, 17 and 18 improved and figure 7 corrected;
the abstract and introduction improved and to appear in CQG | Class.Quant.Grav.25:075001,2008 | 10.1088/0264-9381/25/7/075001 | null | hep-th | null | Starting from the N=1 SU(N_c) x SU(N_c') gauge theory with fundamental and
bifundamental flavors, we apply the Seiberg dual to the first gauge group and
obtain the N=1 dual gauge theory with dual matters including the gauge
singlets. By analyzing the F-term equations of the superpotential, we describe
the intersecting type IIA brane configuration for the meta-stable
nonsupersymmetric vacua of this gauge theory. By introducing an orientifold
6-plane, we generalize to the case for N=1 SU(N_c) x SO(N_c') gauge theory with
fundamental and bifundamental flavors. Finally, the N=1 SU(N_c) x Sp(N_c')
gauge theory with matters is also described very briefly.
| 2008-11-26 |
0704.0128 | Kim Page | P.A. Evans (1), A.P. Beardmore (1), K.L. Page (1), L.G. Tyler (1),
J.P. Osborne (1), M.R. Goad (1), P.T. O'Brien (1), L. Vetere (2), J. Racusin
(2), D. Morris (2), D.N. Burrows (2), M. Capalbi (3), M. Perri (3), N.
Gehrels (4) and P. Romano (5,6) ((1) University of Leicester, (2)
Pennsylvania State University, (3) ASI Science Data Center, (4) NASA/Goddard
Space Flight Center, (5) INAF-Osservatorio Astronomico di Brera, (6)
Universita' degli Studi di Milano) | An online repository of Swift/XRT light curves of GRBs | 8 pages, 6 figures, Accepted for publication in A&A | null | 10.1051/0004-6361:20077530 | null | astro-ph | null | Context. Swift data are revolutionising our understanding of Gamma Ray
Bursts. Since bursts fade rapidly, it is desirable to create and disseminate
accurate light curves rapidly.
Aims. To provide the community with an online repository of X-ray light
curves obtained with Swift. The light curves should be of the quality expected
of published data, but automatically created and updated so as to be
self-consistent and rapidly available. Methods. We have produced a suite of
programs which automatically generates Swift/XRT light curves of GRBs. Effects
of the damage to the CCD, automatic readout-mode switching and pile-up are
appropriately handled, and the data are binned with variable bin durations, as
necessary for a fading source.
Results. The light curve repository website
(http://www.swift.ac.uk/xrt_curves) contains light curves, hardness ratios and
deep images for every GRB which Swift's XRT has observed. When new GRBs are
detected, light curves are created and updated within minutes of the data
arriving at the UK Swift Science Data Centre.
| 2009-11-13 |
0704.0133 | Dieter Lutz | D. Lutz, E. Sturm, L.J. Tacconi, E. Valiante, M. Schweitzer, H.
Netzer, R. Maiolino, P. Andreani, O. Shemmer, S. Veilleux | PAH emission and star formation in the host of the z~2.56 Cloverleaf QSO | Accepted for publication as an ApJ Letter. 14 pages, 3 figures. | null | 10.1086/518537 | null | astro-ph | null | We report the first detection of the 6.2micron and 7.7micron infrared `PAH'
emission features in the spectrum of a high redshift QSO, from the Spitzer-IRS
spectrum of the Cloverleaf lensed QSO (H1413+117, z~2.56). The ratio of PAH
features and rest frame far-infrared emission is the same as in lower
luminosity star forming ultraluminous infrared galaxies and in local PG QSOs,
supporting a predominantly starburst nature of the Cloverleaf's huge
far-infrared luminosity (5.4E12 Lsun, corrected for lensing). The Cloverleaf's
period of dominant QSO activity (Lbol ~ 7E13 Lsun) is coincident with an
intense (star formation rate ~1000 Msun/yr) and short (gas exhaustion time
~3E7yr) star forming event.
| 2009-11-13 |
0704.0135 | Nicolas Menicucci | Nicolas C. Menicucci and G. J. Milburn | A Single Trapped Ion as a Time-Dependent Harmonic Oscillator | 5 pages (two-column format), no figures, added introductory material,
other minor content revisions | Phys. Rev. A 76, 052105 (2007) | 10.1103/PhysRevA.76.052105 | null | quant-ph | null | We show how a single trapped ion may be used to test a variety of important
physical models realized as time-dependent harmonic oscillators. The ion itself
functions as its own motional detector through laser-induced electronic
transitions. Alsing et al. [Phys. Rev. Lett. 94, 220401 (2005)] proposed that
an exponentially decaying trap frequency could be used to simulate (thermal)
Gibbons-Hawking radiation in an expanding universe, but the Hamiltonian used
was incorrect. We apply our general solution to this experimental proposal,
correcting the result for a single ion and showing that while the actual
spectrum is different from the Gibbons-Hawking case, it nevertheless shares an
important experimental signature with this result.
| 2007-12-23 |
0704.0137 | Suresh Tiwari dr | S C Tiwari | Topological defects, geometric phases, and the angular momentum of light | No figures | Optik-International Journal for Light and Electron Optics, 120,
414-417 (2009) | null | null | quant-ph | null | Recent reports on the intriguing features of vector vortex bearing beams are
analyzed using geometric phases in optics. It is argued that the spin
redirection phase induced circular birefringence is the origin of topological
phase singularities arising in the inhomogeneous polarization patterns. A
unified picture of recent results is presented based on this proposition.
Angular momentum shift within the light beam (OAM) has exact equivalence with
the angular momentum holonomy associated with the geometric phase consistent
with our conjecture.
| 2009-05-15 |
0704.0139 | Barbara Lanzoni | B. Lanzoni (1,2), E. Dalessandro (1,2), F.R. Ferraro (1), C. Mancini
(3), G. Beccari (2,4,5), R.T. Rood (6), M. Mapelli (7), S. Sigurdsson (8) (1
Dip. Astro., Bologna; 2 INAF--Oss. Astro., Bologna, 3 Dip. Astro. e Scienza
dello Spazio, Firenze; 4 Dip. di Scienze della Comunicazione, Teramo; 5
INAF--Oss. Astro. di Collurania, Teramo; 6 Dep. of Astronomy and
Astrophysics, The Pennsylvania State University; 7 S.I.S.S.A., Via Beirut 2 -
4, Trieste; 8 Astronomy Department, University of Virginia) | The Blue Straggler Population of the Globular Cluster M5 | ApJ accepted | Astrophys.J.663:267-276,2007 | 10.1086/518592 | null | astro-ph | null | By combining high-resolution HST and wide-field ground based observations, in
ultraviolet and optical bands, we study the Blue Stragglers Star (BSS)
population of the galactic globular cluster M5 (NGC 5904) from its very central
regions up to its periphery. The BSS distribution is highly peaked in the
cluster center, decreases at intermediate radii and rises again outward. Such a
bimodal distribution is similar to those previously observed in other globular
clusters (M3, 47Tucanae, NGC6752). As for these clusters, dynamical simulations
suggest that, while the majority of BSS in M5 could be originated by stellar
collisions, a significant fraction (20-40%) of BSS generated by mass transfer
processes in primordial binaries is required to reproduce the observed radial
distribution. A candidate BSS has been detected beyond the cluster tidal
radius. If confirmed, this could represent an interesting case of an
"evaporating" BSS.
| 2009-06-23 |
0704.0140 | Mariano Cadoni | Mariano Cadoni | Entanglement entropy of two-dimensional Anti-de Sitter black holes | 6 pages, 2 figures, typos corrected | Phys.Lett.B653:434-438,2007 | 10.1016/j.physletb.2007.08.026 | null | hep-th | null | Using the AdS/CFT correspondence we derive a formula for the entanglement
entropy of the anti-de Sitter black hole in two spacetime dimensions. The
leading term in the large black hole mass expansion of our formula reproduces
exactly the Bekenstein-Hawking entropy S_{BH}, whereas the subleading term
behaves as ln S_{BH}. This subleading term has the universal form typical for
the entanglement entropy of physical systems described by effective conformal
fields theories (e.g. one-dimensional statistical models at the critical
point). The well-known form of the entanglement entropy for a two-dimensional
conformal field theory is obtained as analytic continuation of our result and
is related with the entanglement entropy of a black hole with negative mass.
| 2008-11-26 |
0704.0141 | Serguei Molodtsov | S.V. Molodtsov, G.M. Zinovjev | Towards self-consistent definition of instanton liquid parameters | 11 pages, 4 figures | JHEP 0812:112,2008 | 10.1088/1126-6708/2008/12/112 | null | hep-ph | null | The possibility of self-consistent determination of instanton liquid
parameters is discussed together with the definition of optimal pseudo-particle
configurations and comparing the various pseudo-particle ensembles. The
weakening of repulsive interactions between pseudo-particles is argued and
estimated.
| 2009-01-09 |
0704.0143 | Serguei Molodtsov | S.V. Molodtsov, G.M. Zinovjev | Instanton Liquid at Finite Temperature and Chemical Potential of Quarks | 9 pages, 2 figures | Phys.Part.Nucl.Lett.4:11-17,2007;
PismaFiz.Elem.Chast.Atom.Yadra2007N1:25-35,2007 | 10.1134/S1547477107010037 | null | hep-ph | null | Instanton liquid in heated and strongly interacting matter is studied using
the variational principle. The dependence of the instanton liquid density
(gluon condensate) on the temperature and the quark chemical potential is
determined under the assumption that, at finite temperatures, the dominant
contribution is given by an ensemble of calorons. The respective one-loop
effective quark Lagrangian is used.
| 2008-11-26 |
0704.0155 | Floris van der Tak | Floris van der Tak (SRON Groningen), John Black (Onsala), Fredrik
Schoeier (Stockholm), David Jansen and Ewine van Dishoeck (Leiden) | A computer program for fast non-LTE analysis of interstellar line
spectra | Accepted by A&A; 18 A4 pages, 11 figures | null | 10.1051/0004-6361:20066820 | null | astro-ph | null | The large quantity and high quality of modern radio and infrared line
observations require efficient modeling techniques to infer physical and
chemical parameters such as temperature, density, and molecular abundances. We
present a computer program to calculate the intensities of atomic and molecular
lines produced in a uniform medium, based on statistical equilibrium
calculations involving collisional and radiative processes and including
radiation from background sources. Optical depth effects are treated with an
escape probability method. The program is available on the World Wide Web at
http://www.sron.rug.nl/~vdtak/radex/index.shtml . The program makes use of
molecular data files maintained in the Leiden Atomic and Molecular Database
(LAMDA), which will continue to be improved and expanded. The performance of
the program is compared with more approximate and with more sophisticated
methods. An Appendix provides diagnostic plots to estimate physical parameters
from line intensity ratios of commonly observed molecules. This program should
form an important tool in analyzing observations from current and future radio
and infrared telescopes.
| 2015-05-13 |
0704.0156 | Han He | Han He, Huaning Wang | Nonlinear force-free coronal magnetic field extrapolation scheme based
on the direct boundary integral formulation | This paper has been withdrawn by the authors. This paper has been
accepted for publication in JGR-Space Physics. The latest and complete
version of the papaer can be downloaded from
http://rwcc.bao.ac.cn:8001/swap/NLFFF_DBIE_code/HeHan_NLFFF_JGR.pdf (3.76 MB
pdf file) | null | 10.1029/2007JA012441 | null | astro-ph | null | This paper has been withdrawn by the authors.
| 2015-05-13 |
0704.0160 | Grazyna Stasinska | G. Stasinska, G. Tenorio-Tagle, M. Rodriguez, W. J. Henney | Oxygen-rich droplets and the enrichment of the ISM | 4 pages, 5 colour figures, to be published in the proceedings of the
conference "The Metal-Rich Universe", Cambridge University Press | null | null | null | astro-ph | null | We argue that the discrepancies observed in HII regions between abundances
derived from optical recombination lines (ORLs) and collisionally excited lines
(CELs) might well be the signature of a scenario of the enrichment of the
interstellar medium (ISM) proposed by Tenorio-Tagle (1996). In this scenario,
the fresh oxygen released during massive supernova explosions is confined
within the hot superbubbles as long as supernovae continue to explode. Only
after the last massive supernova explosion, the metal-rich gas starts cooling
down and falls on the galaxy within metal-rich droplets. Full mixing of these
metal-rich droplets and the ISM occurs during photoionization by the next
generations of massive stars. During this process, the metal-rich droplets give
rise to strong recombination lines of the metals, leading to the observed
ORL-CEL discrepancy. (The full version of this work is submitted to Astronomy
and Astrophysics.)
| 2007-05-23 |
0704.0166 | I\~naki Garc\'ia-Etxebarria | Inaki Garcia-Etxebarria, Fouad Saad, Angel M. Uranga | Supersymmetry breaking metastable vacua in runaway quiver gauge theories | 26 pages + appendices, 25 figures. v2: Added some acknowledgments | JHEP 0705:047,2007 | 10.1088/1126-6708/2007/05/047 | IFT-UAM/CSIC-07-14, CERN-PH-TH/2007-063 | hep-th | null | In this paper we consider quiver gauge theories with fractional branes whose
infrared dynamics removes the classical supersymmetric vacua (DSB branes). We
show that addition of flavors to these theories (via additional non-compact
branes) leads to local meta-stable supersymmetry breaking minima, closely
related to those of SQCD with massive flavors. We simplify the study of the
one-loop lifting of the accidental classical flat directions by direct
computation of the pseudomoduli masses via Feynman diagrams. This new approach
allows to obtain analytic results for all these theories. This work extends the
results for the $dP_1$ theory in hep-th/0607218. The new approach allows to
generalize the computation to general examples of DSB branes, and for arbitrary
values of the superpotential couplings.
| 2009-11-13 |
0704.0167 | Jan O. Eeg | Jan O. Eeg | Low Energy Aspects of Heavy Meson Decays | 10 pages, 10 figures. Presented at the final Euridice meeting in
Kazimierz, Poland 24-27th of august 2006 | ActaPhys.Polon.B38:2869-2878,2007 | null | null | hep-ph | null | I discuss low energy aspects of heavy meson decays, where there is at least
one heavy meson in the final state. Examples are $B -\bar{B}$ mixing, $B \to D
\bar{D}$, $B \to D \eta'$, and $B \to D \gamma$. %and $B \to D W $ (Isgur-Wise
function). The analysis is performed in the heavy quark limit within
heavy-light chiral perturbation theory. Coefficients of $1/N_c$ suppressed
chiral Lagrangian terms (beyond factorization) have been estimated by means of
a heavy-light chiral quark model.
| 2008-11-26 |
0704.0168 | Paul Dempsey | Paul Dempsey and Peter Duffy | Radiative losses and cut-offs of energetic particles at relativistic
shocks | 10 pages, 23 figures and 2 tables. Accepted for publication by MNRAS. | Mon.Not.Roy.Astron.Soc.378:625-634,2007 | 10.1111/j.1365-2966.2007.11800.x | null | astro-ph | null | We investigate the acceleration and simultaneous radiative losses of
electrons in the vicinity of relativistic shocks. Particles undergo pitch angle
diffusion, gaining energy as they cross the shock by the Fermi mechanism and
also emitting synchrotron radiation in the ambient magnetic field. A
semi-analytic approach is developed which allows us to consider the behaviour
of the shape of the spectral cut-off and the variation of that cut-off with the
particle pitch angle. The implications for the synchrotron emission of
relativistic jets, such as those in gamma ray burst sources and blazars, are
discussed.
| 2009-06-23 |
0704.0169 | Giorgio Calucci | Giorgio Calucci | Very strong and slowly varying magnetic fields as source of axions | 8 pages, no figures | Phys.Rev.D75:097303,2007 | 10.1103/PhysRevD.75.097303 | null | hep-ph | null | The investigation on the production of particles in slowly varying but
extremely intense magnetic field in extended to the case of axions. The
motivation is, as for some previously considered cases, the possibility that
such kind of magnetic field may exist around very compact astrophysical
objects.
| 2008-11-26 |
0704.0171 | Jim Hinton | F. Aharonian, et al | Discovery of a point-like very-high-energy gamma-ray source in Monoceros | 5 pages, 4 figures, to appear in A&A | null | 10.1051/0004-6361:20077299 | null | astro-ph | null | The complex Monoceros Loop SNR/Rosette Nebula region contains several
potential sources of very-high-energy (VHE) gamma-ray emission and two as yet
unidentified high-energy EGRET sources. Sensitive VHE observations are required
to probe acceleration processes in this region. The H.E.S.S. telescope array
has been used to search for very high-energy gamma-ray sources in this region.
CO data from the NANTEN telescope were used to map the molecular clouds in the
region, which could act as target material for gamma-ray production via
hadronic interactions. We announce the discovery of a new gamma-ray source,
HESS J0632+058, located close to the rim of the Monoceros SNR. This source is
unresolved by H.E.S.S. and has no clear counterpart at other wavelengths but is
possibly associated with the weak X-ray source 1RXS J063258.3+054857, the
Be-star MWC 148 and/or the lower energy gamma-ray source 3EG J0634+0521. No
evidence for an associated molecular cloud was found in the CO data.
| 2009-11-13 |
0704.0179 | Marco Bellini | Alessandro Zavatta, Valentina Parigi, and Marco Bellini | Experimental nonclassicality of single-photon-added thermal light states | 7 pages, 6 figures, accepted for publication in Phys. Rev. A | PHYSICAL REVIEW A 75, 052106 (2007) | 10.1103/PhysRevA.75.052106 | null | quant-ph | null | We report the experimental realization and tomographic analysis of novel
quantum light states obtained by exciting a classical thermal field by a single
photon. Such states, although completely incoherent, possess a tunable degree
of quantumness which is here exploited to put to a stringent experimental test
some of the criteria proposed for the proof and the measurement of state
non-classicality. The quantum character of the states is also given in quantum
information terms by evaluating the amount of entanglement that they can
produce.
| 2009-11-13 |
0704.0184 | Paolo Padovani | P. Padovani (ESO) | Gamma-ray emitting AGN and GLAST | 5 pages, 1 figure, invited talk at the First GLAST Symposium,
February 5-8, 2007, Stanford University, USA, to appear in the proceedings | AIP Conf.Proc.921:19-23,2007 | 10.1063/1.2757258 | null | astro-ph | null | I describe the different classes of Active Galactic Nuclei (AGN) and the
basic tenets of unified schemes. I then review the properties of the
extragalactic sources detected in the GeV and TeV bands, showing that the vast
majority of them belong to the very rare blazar class. I further discuss the
kind of AGN GLAST is likely to detect, making some predictions going from the
obvious to the likely, all the way to the less probable.
| 2009-06-23 |
0704.0186 | Ryo Takahasi | Ryo Takahashi and Morimitsu Tanimoto | Dark energy and neutrino model in SUSY -- Remarks on active and sterile
neutrinos mixing -- | 12 pages, 7 figures, to appear in the proceedings of International
Workshop on Neutrino Masses and Mixings -- Toward Unified Understanding of
Quark and Lepton Mass Matrices --, Shizuoka, Japan, 17-19 Dec 2006 | Int.J.Mod.Phys.E16:1529-1540,2007 | 10.1142/S0218301307006861 | null | hep-ph | null | We consider a Mass Varying Neutrinos (MaVaNs) model in supersymmetric theory.
The model includes effects of supersymmetry breaking transmitted by the
gravitational interaction from the hidden sector, in which supersymmetry was
broken, to the dark energy sector. Then evolutions of the neutrino mass and the
equation of state parameter of the dark energy are presented in the model. It
is remarked that only the mass of a sterile neutrino is variable in the case of
the vanishing mixing between the left-handed and a sterile neutrino on
cosmological time scale. The finite mixing makes the mass of the left-handed
neutrino variable.
| 2008-11-26 |
0704.0187 | Gabor Worseck | G. Worseck (1), C. Fechner (2,3), L. Wisotzki (1) and A. Dall'Aglio
(1) ((1) Astrophysikalisches Institut Potsdam, (2) Hamburger Sternwarte, (3)
Universit\"at Potsdam) | The transverse proximity effect in spectral hardness on the line of
sight towards HE 2347-4342 | 15 pages, 11 figures, accepted by A&A, major revision of Section 5
following the referee's comments | Astron.Astrophys. 473 (2007) 805 | 10.1051/0004-6361:20077585 | null | astro-ph | null | We report the discovery of 14 quasars in the vicinity of HE2347-4342, one of
the two quasars whose intergalactic HeII forest has been resolved with FUSE. By
analysing the HI and the HeII opacity variations separately, no transverse
proximity effect is detected near three foreground quasars of HE2347-4342:
QSOJ23503-4328 (z=2.282, $\vartheta=3.59$ arcmin), QSOJ23500-4319 (z=2.302,
$\vartheta=8.77$ arcmin) and QSOJ23495-4338 (z=2.690, $\vartheta=16.28$
arcmin). This is primarily due to line contamination and overdensities probably
created by large-scale structure. By comparing the HI absorption and the
corresponding HeII absorption, we estimated the fluctuating spectral shape of
the extragalactic UV radiation field along this line of sight. We find that the
UV spectral shape near HE2347-4342 and in the projected vicinity of the three
foreground quasars is statistically harder than expected from UV background
models dominated by quasars. In addition, we find three highly ionised metal
line systems near the quasars. However, they do not yield further constraints
on the shape of the ionising field. We conclude that the foreground quasars
show a transverse proximity effect that is detectable as a local hardening of
the UV radiation field, although the evidence is strongest for QSOJ23495-4338.
Thus, the relative spectral hardness traces the proximity effect also in
overdense regions prohibiting the traditional detection in the HI forest.
Furthermore, we emphasise that softening of quasar radiation by radiative
transfer in the intergalactic medium is important to understand the observed
spectral shape variations. From the transverse proximity effect of
QSOJ23495-4338 we obtain a lower limit on the quasar lifetime of ~25 Myr.
| 2011-11-09 |
0704.0192 | Karen O'Neil | K. O'Neil, S. Oey, G. Bothun | Star Formation in Galaxies with Large Lower Surface Brightness Disks | 50 pages; Full paper with all figures available at
http://www.gb.nrao.edu/~koneil; Accepted by AJ | null | 10.1086/518831 | null | astro-ph | null | We present B, R, and Halpha imaging data of 19 large disk galaxies whose
properties are intermediate between classical low surface brightness galaxies
and ordinary high surface brightness galaxies. We use data taken from the
Lowell 1.8m Perkins telescope to determine the galaxies' overall morphology,
color, and star formation properties. Morphologically, the galaxies range from
Sb through Irr and include galaxies with and without nuclear bars. The colors
of the galaxies vary from B-R = 0.3 - 1.9, and most show at least a slight
bluing of the colors with increasing radius. The Halpha images of these
galaxies show an average star formation rate lower than is found for similar
samples with higher surface brightness disks. Additionally, the galaxies
studied have both higher gas mass-to-luminosity and diffuse Halpha emission
than is found in higher surface brightness samples.
| 2009-11-13 |
0704.0196 | Michal Praszalowicz | Karolina Piesciuk, Michal Praszalowicz | Remarks on N_c dependence of decays of exotic baryons | 8 pages, 6 figures to be published in proceedings of YKIS06 in
Progress of Theoretical Physics. In v2 minor typos corrected | Prog.Theor.Phys.Suppl.168:70-77,2007 | 10.1143/PTPS.168.70 | TPJU-03/2007 | hep-ph | null | We calculate the N_c dependence of the decay widths of exotic eikosiheptaplet
within the framework of Chral Quark Soliton Model. We also discuss
generalizations of regular baryon representations for arbitrary N_c.
| 2008-11-26 |
0704.0202 | Simon Perdrix | Simon Perdrix | Towards Minimal Resources of Measurement-based Quantum Computation | 8 pages | New J. Phys. 9 206 (2007) | 10.1088/1367-2630/9/6/206 | null | quant-ph | null | We improve the upper bound on the minimal resources required for
measurement-based quantum computation. Minimizing the resources required for
this model is a key issue for experimental realization of a quantum computer
based on projective measurements. This new upper bound allows also to reply in
the negative to the open question about the existence of a trade-off between
observable and ancillary qubits in measurement-based quantum computation.
| 2007-09-20 |
0704.0203 | August Muench | August A. Muench, Charles J. Lada, K. L. Luhman, James Muzerolle and
Erick Young | A Spitzer census of the IC 348 nebula | Accepted to AJ; 33 pages in emulateapj format. | Astron.J.134:411-444,2007 | 10.1086/518560 | null | astro-ph | null | We present a Spitzer based census of the IC 348 nebula and embedded star
cluster. Our Spitzer census supplemented by ground based spectra has added 42
class II T-Tauri sources to the cluster membership and identified ~20 class 0/I
protostars. The population of IC 348 likely exceeds 400 sources after
accounting statistically for unidentified diskless members. Our Spitzer census
of IC 348 reveals a population of protostars that is anti-correlated spatially
with the T-Tauri members, which comprise the centrally condensed cluster around
a B star. The protostars are instead found mostly at the cluster periphery
about 1 pc from the B star and spread out along a filamentary ridge. We find
that the star formation rate in this protostellar ridge is consistent with that
rate which built the exposed cluster while the presence of fifteen cold,
starless, millimeter cores intermingled with this protostellar population
indicates that the IC 348 nebula has yet to finish forming stars. We show that
the IC 348 cluster is of order 3-5 crossing times old, and, as evidenced by its
smooth radial profile and confirmed mass segregation, is likely relaxed. While
it seems apparent that the current cluster configuration is the result of
dynamical evolution and its primordial structure has been erased, our findings
support a model where embedded clusters are built up from numerous smaller
sub-clusters. Finally, the results of our Spitzer census indicate that the
supposition that star formation must progress rapidly in a dark cloud should
not preclude these observations that show it can be relatively long lived.
| 2009-06-23 |
0704.0205 | Paolo Esposito | P. Esposito, A. Tiengo, A. De Luca, F. Mattana | Discovery of X-ray emission from the young radio pulsar PSR J1357-6429 | Revised version (minor changes in text and figures). Accepted for
publication on Astronomy and Astrophysics Letters on 10/04/2007 | Astronomy and Astrophysics, Volume 467, Issue 2, May IV 2007,
pp.L45-L48 | 10.1051/0004-6361:20077480 | null | astro-ph | null | We present the first X-ray detection of the very young pulsar PSR J1357-6429
(characteristic age of 7.3 kyr) using data from the XMM-Newton and Chandra
satellites. We find that the spectrum is well described by a power-law plus
blackbody model, with photon index Gamma=1.4 and blackbody temperature kT=160
eV. For the estimated distance of 2.5 kpc, this corresponds to a 2-10 keV
luminosity of about 1.2E+32 erg/s, thus the fraction of the spin-down energy
channeled by PSR J1357-6429 into X-ray emission is one of the lowest observed.
The Chandra data confirm the positional coincidence with the radio pulsar and
allow to set an upper limit of 3E+31 erg/s on the 2-10 keV luminosity of a
compact pulsar wind nebula. We do not detect any pulsed emission from the
source and determine an upper limit of 30% for the modulation amplitude of the
X-ray emission at the radio frequency of the pulsar.
| 2009-02-23 |
0704.0209 | Sangwook Park | Sangwook Park, David N. Burrows, Gordon P. Garmire (Penn State),
Richard McCray (Colorado), Judith L. Racusin (Penn State), Svetozar A. Zhekov
(Space Res Inst) | Chandra Observations of Supernova 1987A | 8 pages, 4 figures (including 2 color figs), 3 tables. To appear in
the proceedings of "Supernova 1987A: 20 Years after Supernovae and Gamma-Ray
Bursters", held in Aspen CO. USA, Feb 19-23, 2007 | AIP Conf.Proc.937:43-50,2007 | 10.1063/1.2803606 | null | astro-ph | null | We have been monitoring Supernova (SN) 1987A with {\it Chandra X-Ray
Observatory} since 1999. We present a review of previous results from our {\it
Chandra} observations, and some preliminary results from new {\it Chandra} data
obtained in 2006 and 2007. High resolution imaging and spectroscopic studies of
SN 1987A with {\it Chandra} reveal that X-ray emission of SN 1987A originates
from the hot gas heated by interaction of the blast wave with the ring-like
dense circumstellar medium (CSM) that was produced by the massive progenitor's
equatorial stellar winds before the SN explosion. The blast wave is now
sweeping through dense CSM all around the inner ring, and thus SN 1987A is
rapidly brightening in soft X-rays. At the age of 20 yr (as of 2007 January),
X-ray luminosity of SN 1987A is $L_{\rm X}$ $\sim$ 2.4 $\times$ 10$^{36}$ ergs
s$^{-1}$ in the 0.5$-$10 keV band. X-ray emission is described by two-component
plane shock model with electron temperatures of $kT$ $\sim$ 0.3 and 2 keV. As
the shock front interacts with dense CSM all around the inner ring, the X-ray
remnant is now expanding at a much slower rate of $v$ $\sim$ 1400 km s$^{-1}$
than it was until 2004 ($v$ $\sim$ 6000 km s$^{-1}$).
| 2009-06-23 |
0704.0219 | Joseph Gelfand | Joseph D. Gelfand, B. M. Gaensler, Patrick O. Slane, Daniel J.
Patnaude, John P. Hughes, Fernando Camilo | The Radio Emission, X-ray Emission, and Hydrodynamics of G328.4+0.2: A
Comprehensive Analysis of a Luminous Pulsar Wind Nebula, its Neutron Star,
and the Progenitor Supernova Explosion | 27 pages, 11 figures, accepted for publication in The Astrophysical
Journal | Astrophys.J.663:468-486,2007 | 10.1086/518498 | null | astro-ph | null | We present new observational results obtained for the Galactic non-thermal
radio source G328.4+0.2 to determine both if this source is a pulsar wind
nebula or supernova remnant, and in either case, the physical properties of
this source. Using X-ray data obtained by XMM, we confirm that the X-ray
emission from this source is heavily absorbed and has a spectrum best fit by a
power law model of photon index=2 with no evidence for a thermal component, the
X-ray emission from G328.4+0.2 comes from a region significantly smaller than
the radio emission, and that the X-ray and radio emission are significantly
offset from each other. We also present the results of a new high resolution (7
arcseconds) 1.4 GHz image of G328.4+0.2 obtained using the Australia Telescope
Compact Array, and a deep search for radio pulsations using the Parkes Radio
Telescope. We find that the radio emission has a flat spectrum, though some
areas along the eastern edge of G328.4+0.2 have a steeper radio spectral index
of ~-0.3. Additionally, we obtain a luminosity limit of the central pulsar of
L_{1400} < 30 mJy kpc^2, assuming a distance of 17 kpc. In light of these
observational results, we test if G328.4+0.2 is a pulsar wind nebula (PWN) or a
large PWN inside a supernova remnant (SNR) using a simple hydrodynamic model
for the evolution of a PWN inside a SNR. As a result of this analysis, we
conclude that G328.4+0.2 is a young (< 10000 years old) pulsar wind nebula
formed by a low magnetic field (<10^12 G) neutron star born spinning rapidly
(<10 ms) expanding into an undetected SNR formed by an energetic (>10^51 ergs),
low ejecta mass (M < 5 Solar Masses) supernova explosion which occurred in a
low density (n~0.03 cm^{-3}) environment.
| 2009-06-23 |
0704.0222 | Miguel \'Angel S\'anchez-Conde Mr. | Miguel A. Sanchez-Conde | Dark Matter annihilation in Draco: new considerations on the expected
gamma flux | 2 pages, 2 figures, to appear in the Proceedings of the First
International GLAST Symposium, Stanford University, 5-8 February 2007 | AIP Conf.Proc.921:510-511,2007 | 10.1063/1.2757426 | null | astro-ph | null | A new estimation of the gamma-ray flux that we expect to detect from SUSY
dark matter annihilation from the Draco dSph is presented using the DM density
profiles compatible with the latest observations. This calculation takes also
into account the important effect of the Point Spread Function (PSF) of the
telescope. We show that this effect is crucial in the way we will observe and
interpret a possible signal detection. Finally, we discuss the prospects to
detect a possible gamma signal from Draco for MAGIC and GLAST.
| 2009-06-23 |
0704.0223 | Fu-Yan Bian | Yu-Qing Lou (1,2,3) and Wei-Gang Wang (1), ((1) Tsinghua Center For
astrophysics, Tsinghua University, (2)The University of Chicago, (3) National
Astronomical Observatories, Chinese Academy of Science.) | Magnetohydrodynamic Rebound Shocks of Supernovae | 5 pages, 1 figure, Accepted for publication in MNRAS | Mon.Not.Roy.Astron.Soc.Lett.378:L54-L58,2007 | 10.1111/j.1745-3933.2007.00319.x | null | astro-ph | null | We construct magnetohydrodynamic (MHD) similarity rebound shocks joining
`quasi-static' asymptotic solutions around the central degenerate core to
explore an MHD model for the evolution of random magnetic field in supernova
explosions. This provides a theoretical basis for further studying synchrotron
diagnostics, MHD shock acceleration of cosmic rays, and the nature of intense
magnetic field in compact objects. The magnetic field strength in space
approaches a limiting ratio, that is comparable to the ratio of the ejecta mass
driven out versus the progenitor mass, during this self-similar rebound MHD
shock evolution. The intense magnetic field of the remnant compact star as
compared to that of the progenitor star is mainly attributed to both the
gravitational core collapse and the radial distribution of magnetic field.
| 2009-06-23 |
0704.0225 | Alexander Kashlinsky | A. Kashlinsky and D. Band | Exploring First Stars Era with GLAST | to appear in Proceedings of 1st International GLAST Symposium | AIP Conf.Proc.921:243-245,2007 | 10.1063/1.2757312 | null | astro-ph | null | Cosmic infrared background (CIB) includes emissions from objects inaccessible
to current telescopic studies, such as the putative Population III, the first
stars. Recently, strong direct evidence for significant CIB levels produced by
the first stars came from CIB fluctuations discovered in deep Spitzer images.
Such CIB levels should have left a unique absorption feature in the spectra of
high-z GRBs and blazars as suggested in [4]. This is observable with GLAST
sources at z>2 and measuring this absorption will give important information on
energetics and constituents of the first stars era.
| 2009-06-23 |
0704.0226 | Francesco Tombesi | F. Tombesi (1,2), B. De Marco (3), K. Iwasawa (4), M. Cappi (1), M.
Dadina (1), G. Ponti (1,2), G. Miniutti (5) and G.G.C. Palumbo (2) ((1)
INAF-IASF Bologna, (2) UNIBO, (3) SISSA, (4) MPE, (5) Institute of Astronomy,
Cambridge) | Correlated modulation between the redshifted Fe K alpha line and the
continuum emission in NGC 3783 | 8 pages, 7 figures, to be published in Astronomy and Astrophysics | null | 10.1051/0004-6361:20066713 | null | astro-ph | null | It has been suggested that X-ray observations of rapidly variable Seyfert
galaxies may hold the key to probe the gas orbital motions in the innermost
regions of accretion discs around black holes and, thus, trace flow patterns
under the effect of the hole strong gravitational field. We explore this
possibility analizing XMM-Newton observations of the seyfert 1 galaxy NGC 3783.
A detiled time-resolved spectral analysis is performed down to the shortest
possible time-scales (few ks) using "excess maps" and cross-correlating light
curves in different energy bands. In addition to a constant core of the Fe K
alpha line, we detected a variable and redshifted Fe K alpha emission feature
between 5.3-6.1 keV. The line exhibits a modulation on a time-scale of 27 ks
that is similar to and in phase with a modulation of the 0.3-10 keV source
continuum. The time-scale of the correlated variability of the redshifted Fe
line and continuum agrees with the local dynamical time-scale of the accretion
disc at 10 r_g around a black hole of 10^7 M_sun. Given the shape of the
redshfted line emission and the overall X-ray variability pattern, the line is
likely to arise from the relativistic region near the black hole.
| 2009-11-13 |
0704.0230 | Rene Duffard | R. Duffard and F. Roig | Two new basaltic asteroids in the Outer Main Belt? | 13 pages, 3 figures, 2 tables | null | null | null | astro-ph | null | The identification of basaltic asteroids in the asteroid Main Belt and the
description of their surface mineralogy is necessary to understand the
diversity in the collection of basaltic meteorites. Basaltic asteroids can be
identified from their visible reflectance spectra and are classified as V-type
in the usual taxonomies. In this work, we report visible spectroscopic
observations of two candidate V-type asteroids, (7472) Kumakiri and (10537)
1991 RY16, located in the outer Main Belt (a > 2.85 UA). These candidate have
been previously identified by Roig and Gil-Hutton (2006, Icarus 183, 411) using
the Sloan Digital Sky Survey colors. The spectroscopic observations have been
obtained at the Calar Alto Observatory, Spain, during observational runs in
November and December 2006. The spectra of these two asteroids show the steep
slope shortwards of 0.70 microns and the deep absorption feature longwards of
0.75 microns that are characteristic of V-type asteroids. However, the presence
of a shallow but conspicuous absorption band around 0.65 microns opens some
questions about the actual mineralogy of these two asteroids. Such band has
never been observed before in basaltic asteroids with the intensity we detected
it. We discuss the possibility for this shallow absorption feature to be caused
by the presence of chromium on the asteroid surface. Our results indicate that,
together with (1459) Magnya, asteroids (7472) Kumakiri and (10537) 1991 RY16
may be the only traces of basaltic material found up to now in the outer Main
Belt.
| 2008-01-14 |
0704.0232 | Christoph Bergbauer | Christoph Bergbauer, Dirk Kreimer | New algebraic aspects of perturbative and non-perturbative Quantum Field
Theory | 15 pages, Contribution to the Proceedings of the ICMP 2006, 2 typos
corrected, final version | in "New Trends in Mathematical Physics; Selected contributions of
the XVth International Congress on Mathematical Physics", V. Sidoravicius
(Ed.), Springer (2009) | null | null | hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this expository article we review recent advances in our understanding of
the combinatorial and algebraic structure of perturbation theory in terms of
Feynman graphs, and Dyson-Schwinger equations. Starting from Lie and Hopf
algebras of Feynman graphs, perturbative renormalization is rephrased
algebraically. The Hochschild cohomology of these Hopf algebras leads the way
to Slavnov-Taylor identities and Dyson-Schwinger equations. We discuss recent
progress in solving simple Dyson-Schwinger equations in the high energy sector
using the algebraic machinery. Finally there is a short account on a relation
to algebraic geometry and number theory: understanding Feynman integrals as
periods of mixed (Tate) motives.
| 2009-11-04 |
0704.0234 | Gabriele Ghisellini | G. Ghirlanda (1), L. Nava (1,2), G. Ghisellini (1), C. Firmani (1,3)
((1) Osserv. Astr. di Brera, (2) Univ. degli Studi dell'Insubria, (3)
U.N.A.M.) | Comments on ``Are Swift Gamma-Ray Bursts consistent with the Ghirlanda
relation?", by Campana et al.(astro--ph/0703676) | 3 pages | null | null | null | astro-ph | null | In their recent paper, Campana et al. (2007) found that 5 bursts, among those
detected by Swift, are outliers with respect to the E_peak-E_gamma
("Ghirlanda") correlation. We instead argue that they are not.
| 2007-05-23 |
0704.0237 | Christopher W. Mauche | Christopher W. Mauche, Duane A. Liedahl, Shizuka Akiyama (Lawrence
Livermore Nat'l Lab.), Tomasz Plewa (University of Chicago) | Hydrodynamic and Spectral Simulations of HMXB Winds | 4 pages including 2 color encapsulated postscript figures; LaTeX
format, uses ptptex.cls; submitted for inclusion in the proceedings of "The
Extreme Universe in the Suzaku Era" conference, to be published in Progress
of Theoretical Physics, Supplement. | Prog.Theor.Phys.Suppl.169:196-199,2007 | 10.1143/PTPS.169.196 | null | astro-ph | null | We describe preliminary results of a global model of the radiatively-driven
photoionized wind and accretion flow of the high-mass X-ray binary Vela X-1.
The full model combines FLASH hydrodynamic calculations, XSTAR photoionization
calculations, HULLAC atomic data, and Monte Carlo radiation transport. We
present maps of the density, temperature, velocity, and ionization parameter
from a FLASH two-dimensional time-dependent simulation of Vela X-1, as well as
maps of the emissivity distributions of the X-ray emission lines.
| 2009-06-23 |
0704.0238 | Geoffrey C. Bower | Geoffrey C. Bower (Berkeley), Alberto Bolatto (Berkeley), Eric Ford
(CfA, Florida), Paul Kalas (Berkeley), Jim Ulvestad (NRAO) | Radio Astrometric Detection and Characterization of Extra-Solar Planets:
A White Paper Submitted to the NSF ExoPlanet Task Force | null | null | null | null | astro-ph | null | The extraordinary astrometric accuracy of radio interferometry creates an
important and unique opportunity for the discovery and characterization of
exo-planets. Currently, the Very Long Baseline Array can routinely achieve
better than 100 microarcsecond accuracy, and can approach 10 microarcsecond
with careful calibration. We describe here RIPL, the Radio Interferometric
PLanet search, a new program with the VLBA and the Green Bank 100 m telescope
that will survey 29 low-mass, active stars over 3 years with sub-Jovian planet
mass sensitivity at 1 AU. An upgrade of the VLBA bandwidth will increase
astrometric accuracy by an order of magnitude. Ultimately, the colossal
collecting area of the Square Kilometer Array could push astrometric accuracy
to 1 microarcsecond, making detection and characterizaiton of Earth mass
planets possible.
RIPL and other future radio astrometric planet searches occupy a unique
volume in planet discovery and characterization parameter space. The parameter
space of astrometric searches gives greater sensitivity to planets at large
radii than radial velocity searches. For the VLBA and the expanded VLBA, the
targets of radio astrometric surveys are by necessity nearby, low-mass, active
stars, which cannot be studied efficiently through the radial velocity method,
coronagraphy, or optical interferometry. For the SKA, detection sensitivity
will extend to solar-type stars. Planets discovered through radio astrometric
methods will be suitable for characterization through extreme adaptive optics.
The complementarity of radio astrometric techniques with other methods
demonstrates that radio astrometry can play an important role in the roadmap
for exoplanet discovery and characterization.
| 2007-05-23 |
0704.0240 | Dam Thanh Son | D. T. Son, A. O. Starinets | Viscosity, Black Holes, and Quantum Field Theory | 23 pages, a review. New proof of the universality of the viscosity
entropy ratio, new derivation of Kubo's formula; references added and minor
typos corrected in version 2 | Ann.Rev.Nucl.Part.Sci.57:95-118,2007 | 10.1146/annurev.nucl.57.090506.123120 | INT PUB 07-02 | hep-th | null | We review recent progress in applying the AdS/CFT correspondence to
finite-temperature field theory. In particular, we show how the hydrodynamic
behavior of field theory is reflected in the low-momentum limit of correlation
functions computed through a real-time AdS/CFT prescription, which we
formulate. We also show how the hydrodynamic modes in field theory correspond
to the low-lying quasinormal modes of the AdS black p-brane metric. We provide
a proof of the universality of the viscosity/entropy ratio within a class of
theories with gravity duals and formulate a viscosity bound conjecture.
Possible implications for real systems are mentioned.
| 2008-11-26 |
0704.0242 | Vincent L. Fish | Vincent L. Fish (NRAO) | Masers and star formation | 10 pages, iaus.cls, to appear in IAU Symp. 242 proceedings
(Astrophysical masers and their environments) | null | 10.1017/S1743921307012604 | null | astro-ph | null | Recent observational and theoretical advances concerning astronomical masers
in star forming regions are reviewed. Major masing species are considered
individually and in combination. Key results are summarized with emphasis on
present science and future prospects.
| 2009-11-13 |
0704.0251 | Gilad Gour | Gilad Gour, Nolan R. Wallach | Entanglement of Subspaces and Error Correcting Codes | 8 pages, Published Version | Phys. Rev. A 76, 042309 (2007) | 10.1103/PhysRevA.76.042309 | null | quant-ph | null | We introduce the notion of entanglement of subspaces as a measure that
quantify the entanglement of bipartite states in a randomly selected subspace.
We discuss its properties and in particular we show that for maximally
entangled subspaces it is additive. Furthermore, we show that maximally
entangled subspaces can play an important role in the study of quantum error
correction codes. We discuss both degenerate and non-degenerate codes and show
that the subspace spanned by the logical codewords of a non-degenerate code is
a 2k-totally (maximally) entangled subspace. As for non-degenerate codes, we
provide a mathematical definition in terms of subspaces and, as an example, we
analyze Shor's nine qubits code in terms of 22 mutually orthogonal subspaces.
| 2011-11-09 |
0704.0252 | Ashutosh Alok | Ashutosh Kumar Alok and S. Uma Sankar | Does the present data on B_s - bar B_s mixing rule out a large
enhancement in the branching ratio of B_s --> mu+ mu- ? | 7 pages, no figures | null | null | null | hep-ph | null | In this letter, we consider the constraints imposed by the recent measurement
of B_s - bar B_s mixing on the new physics contribution to the rare decay B_s
--> mu+ mu-. New physics in the form vector and axial-vector couplings is
already severely constrained by the data on B --> (K,K*) mu+ mu-. Here, we show
that B_s - bar B_s mixing data, together with the data on K0 - bar K0 mixing
and K_L --> mu+ mu- decay rate, strongly constrain the scalar-pseudoscalar
contribution to B_s --> mu+ mu-. We conclude that new physics can at best lead
to a factor of 2 increase in the branching ratio of B_s --> mu+ mu- compared to
its Standard Model expectation.
| 2007-05-23 |
0704.0253 | Paul Harvey | Paul M. Harvey, Luisa M. Rebull, Tim Brooke, William J. Spiesman,
Nicholas Chapman, Tracy L. Huard, Neal J. Evans II, Lucas Cieza, Shih-Ping
Lai, Lori E. Allen, Lee G. Mundy, Deborah L. Padgett, Anneila I. Sargent,
Karl R. Stapelfeldt, Philip C. Myers, Ewine F. van Dishoeck, Geoffrey A.
Blake, David W. Koerner | The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds VIII.
Serpens Observed with MIPS | null | Astrophys.J.663:1139-1148,2007 | 10.1086/518647 | null | astro-ph | null | We present maps of 1.5 square degrees of the Serpens dark cloud at 24, 70,
and 160\micron observed with the Spitzer Space Telescope MIPS Camera. More than
2400 compact sources have been extracted at 24um, nearly 100 at 70um, and 4 at
160um. We estimate completeness limits for our 24um survey from Monte Carlo
tests with artificial sources inserted into the Spitzer maps. We compare source
counts, colors, and magnitudes in the Serpens cloud to two reference data sets,
a 0.50 deg^2 set on a low-extinction region near the dark cloud, and a 5.3
deg^2 subset of the SWIRE ELAIS N1 data that was processed through our
pipeline. These results show that there is an easily identifiable population of
young stellar object candidates in the Serpens Cloud that is not present in
either of the reference data sets. We also show a comparison of visual
extinction and cool dust emission illustrating a close correlation between the
two, and find that the most embedded YSO candidates are located in the areas of
highest visual extinction.
| 2010-03-18 |
0704.0254 | Alexandre Alves | Alexandre Alves and Oscar Eboli | Unravelling the sbottom spin at the CERN LHC | 9 pages, 11 figures | Phys.Rev.D75:115013,2007 | 10.1103/PhysRevD.75.115013 | null | hep-ph | null | Establishing that a signal of new physics is undoubtly supersymmetric
requires not only the discovery of the supersymmetric partners but also probing
their spins and couplings. We show that the sbottom spin can be probed at the
CERN Large Hadron Collider using only angular correlations in sbottom pair
production with subsequent decay of sbottoms into bottom quark plus the
lightest neutralino, which allow us to distinguish a universal extra
dimensional interpretation with a fermionic heavy bottom quark from
supersymmetry with a bosonic bottom squark. We demonstrate that this channel
provides a clear indication of the sbottom spin provided the sbottom production
rate and branching ratio into bottom quark plus the lightest neutralino are
sufficiently large to have a clear signal above Standard Model backgrounds.
| 2008-11-26 |
0704.0255 | Felipe Marin | Felipe Marin (Chicago, KICP), Risa Wechsler (KIPAC, Stanford), Joshua
Frieman (Chicago, KICP and Fermilab), Robert Nichol (ICG, Portsmouth) | Modeling the three-point correlation function | 12 pages, 11 figures, ApJ accepted. Corrected typos, minor changes
from referee comments | Astrophys.J.672:849-860,2008 | 10.1086/523628 | null | astro-ph | null | We present new predictions for the galaxy three-point correlation function
(3PCF) using high-resolution dissipationless cosmological simulations of a flat
LCDM Universe which resolve galaxy-size halos and subhalos. We create realistic
mock galaxy catalogs by assigning luminosities and colors to dark matter halos
and subhalos, and we measure the reduced 3PCF as a function of luminosity and
color in both real and redshift space. As galaxy luminosity and color are
varied, we find small differences in the amplitude and shape dependence of the
reduced 3PCF, at a level qualitatively consistent with recent measurements from
the SDSS and 2dFGRS. We confirm that discrepancies between previous 3PCF
measurements can be explained in part by differences in binning choices. We
explore the degree to which a simple local bias model can fit the simulated
3PCF. The agreement between the model predictions and galaxy 3PCF measurements
lends further credence to the straightforward association of galaxies with CDM
halos and subhalos.
| 2008-11-26 |
0704.0256 | Paul Harvey | Paul M. Harvey and Andrew Oldag | Multi-spectral Observations of Lunar Occultations: I. Resolving The Dust
Shell Around AFGL 5440 | null | Astrophys.J.663:543-552,2007 | 10.1086/518588 | null | astro-ph | null | We present observations and modeling of a lunar occultation of the
dust-enshrouded carbon star AFGL 5440. The observations were made over a
continuous range of wavelengths from 1 - 4um with a high-speed
spectrophotometer designed expressly for this purpose. We find that the
occultation fringes cannot be fit by any single-size model. We use the DUSTY
radiative transfer code to model a circumstellar shell and fit both the
observed occultation light curves and the spectral energy distribution
described in the literature. We find a strong constraint on the inner radius of
the dust shell, Tmax = 950 K +/- 50K, and optical depth at 5um of 0.5 +/- 0.1.
The observations are best fit by models with a density gradient of r^-2 or the
gradient derived by Ivezic & Elitzur for a radiatively driven hydrodynamic
outflow. Our models cannot fit the observed IRAS 60um flux without assuming a
substantial abundance of graphite or by assuming a substantially higher
mass-loss rate in the past.
| 2009-11-13 |
0704.0259 | Scott J. Kenyon | Scott J. Kenyon, Benjamin C. Bromley, David P. O'Brien, Donald R.
Davis | Formation and Collisional Evolution of Kuiper Belt Objects | 23 pages, 9 figures, 1 table; to appear in `Transneptunian Objects',
Barucci et al. eds., University of Arizona Press | null | null | null | astro-ph | null | This chapter summarizes analytic theory and numerical calculations for the
formation and collisional evolution of KBOs at 20--150 AU. We describe the main
predictions of a baseline self-stirring model and show how dynamical
perturbations from a stellar flyby or stirring by a giant planet modify the
evolution. Although robust comparisons between observations and theory require
better KBO statistics and more comprehensive calculations, the data are broadly
consistent with KBO formation in a massive disk followed by substantial
collisional grinding and dynamical ejection. However, there are important
problems reconciling the results of coagulation and dynamical calculations.
Contrasting our current understanding of the evolution of KBOs and asteroids
suggests that additional observational constraints, such as the identification
of more dynamical families of KBOs (like the 2003 EL61 family), would provide
additional information on the relative roles of collisional grinding and
dynamical ejection in the Kuiper Belt. The uncertainties also motivate
calculations that combine collisional and dynamical evolution, a `unified'
calculation that should give us a better picture of KBO formation and
evolution.
| 2007-05-23 |
0704.0261 | Scott Randall | Scott W. Randall, Maxim Markevitch, Douglas Clowe, Anthony H.
Gonzalez, and Marusa Bradac | Constraints on the Self-Interaction Cross-Section of Dark Matter from
Numerical Simulations of the Merging Galaxy Cluster 1E 0657-5 | null | null | 10.1086/587859 | null | astro-ph | null | (Abridged) We compare recent results from X-ray, strong lensing, weak
lensing, and optical observations with numerical simulations of the merging
galaxy cluster 1E0657-56. X-ray observations reveal a bullet-like subcluster
with a prominent bow shock, while lensing results show that the positions of
the total mass peaks are consistent with the centroids of the collisionless
galaxies (and inconsistent with the X-ray brightness peaks). Previous studies,
based on older observational datasets, have placed upper limits on the
self-interaction cross-section of dark matter per unit mass, sigma/m, using
simplified analytic techniques. In this work, we take advantage of new,
higher-quality observational datasets by running N-body simulations of
1E0657-56 that include the effects of self-interacting dark matter, and
comparing the results with observations. Furthermore, the recent data allow for
a new independent method of constraining sigma/m, based on the non-observation
of an offset between the bullet subcluster mass peak and galaxy centroid. This
new method places an upper limit (68% confidence) of sigma/m < 1.25 cm^2/g. If
we make the assumption that the subcluster and the main cluster had equal
mass-to-light ratios prior to the merger, we derive our most stringent
constraint of sigma/m < 0.7 cm^2/g, which comes from the consistency of the
subcluster's observed mass-to-light ratio with the main cluster's, and with the
universal cluster value, ruling out the possibility of a large fraction of dark
matter particles being scattered away due to collisions. Our limit is a slight
improvement over the previous result from analytic estimates, and rules out
most of the 0.5 - 5cm^2/g range invoked to explain inconsistencies between the
standard collisionless cold dark matter model and observations.
| 2009-11-13 |
0704.0262 | Matteo Bertolini | Riccardo Argurio, Matteo Bertolini, Gabriele Ferretti, Alberto Lerda
and Christoffer Petersson | Stringy Instantons at Orbifold Singularities | Latex, 29 pages, 6 figures. v3: typos corrected, one comment and refs
added, published version | JHEP 0706:067,2007 | 10.1088/1126-6708/2007/06/067 | null | hep-th | null | We study the effects produced by D-brane instantons on the holomorphic
quantities of a D-brane gauge theory at an orbifold singularity. These effects
are not limited to reproducing the well known contributions of the gauge theory
instantons but also generate extra terms in the superpotential or the
prepotential. On these brane instantons there are some neutral fermionic
zero-modes in addition to the ones expected from broken supertranslations. They
are crucial in correctly reproducing effects which are dual to gauge theory
instantons, but they may make some other interesting contributions vanish. We
analyze how orientifold projections can remove these zero-modes and thus allow
for new superpotential terms. These terms contribute to the dynamics of the
effective gauge theory, for instance in the stabilization of runaway
directions.
| 2009-11-13 |
0704.0265 | Stefano Covino | A. Dolcini, F. Farfanelli, S. Ciprini, A. Treves, S. Covino, G. Tosti,
E. Pian, B. Sbarufatti, E. Molinari, G. Chincarini, F.M. Zerbi, G. Malaspina,
P. Conconi, L. Nicastro, E. Palazzi, V. Testa, F. Vitali, L.A. Antonelli, J.
Danziger, G. Tagliaferri, E. Meurs, S. Vergani, A. Fernandez-Soto, E.
Distefano, G. Cutispoto, F. D'Alessio | REM near-IR and optical multiband observations of PKS2155-304 in 2005 | This paper is the corrected version of the paper published in A&A 469
503. It contains the material in the "Errata Corrrige", in press in A&A | Astron.Astrophys.469:503,2007 | 10.1051/0004-6361:20066477 | null | astro-ph | null | Spectral variability is the main tool for constraining emission models of BL
Lac objects. By means of systematic observations of the BL Lac prototype PKS
2155-304 in the infrared-optical band, we explore variability on the scales of
months, days and hours. We made our observations with the robotic 60 cm
telescope REM located at La Silla, Chile. VRIJHK filters were used. PKS
2155-304 was observed from May to December 2005. The wavelength interval
explored, the total number of photometric points and the short integration time
render our photometry substantially superior to previous ones for this source.
On the basis of the intensity and colour we distinguish three different states
of the source, each of duration of months, which include all those described in
the literature. In particular, we report the highest state ever detected in the
H band. The source varied by a factor of 4 in this band, much more than in the
V band (a factor ~2). The source softened with increasing intensity, contrary
to the general pattern observed in the UV-X-ray bands. On five nights of
November we had nearly continuous monitoring for 2-3 hours. A variability
episode with a time scale of ~24 h is well documented, a much more rapid flare
with t=1-2 h, is also apparent, but is supported by relatively few points.
| 2009-11-16 |
0704.0266 | Jennifer L. Hoffman | Jennifer L. Hoffman | Supernova Polarization and the Type IIn Classification | 5 pages, 4 figures; to appear in "Supernova 1987A: 20 Years After:
Supernovae and Gamma-Ray Bursters", AIP, New York, eds. S. Immler, K.W.
Weiler, and R. McCray. v2: References added, typos corrected, and figures
slightly modified for legibility when reduced in size | AIP Conf.Proc.937:365-369,2007 | 10.1063/1.2803592 | null | astro-ph | null | While the members of the Type IIn category of supernovae are united by the
presence of strong multicomponent Balmer emission lines in their spectra, they
are quite heterogeneous with respect to other properties such as Balmer line
profiles, light curves, strength of radio emission, and intrinsic brightness.
We are now beginning to see variety among SNe IIn in their polarimetric
characteristics as well, some but not all of which may be due to inclination
angle effects. The increasing number of known "hybrid" SNe with IIn-like
emission lines suggests that circumstellar material may be more common around
all types of SNe than previously thought. Investigation of the correlations
between spectropolarimetric signatures and other IIn attributes will help us
address the question of classification of "interacting SNe" and the possibility
of distinguishing different groups within the diverse IIn subclass.
| 2009-06-23 |
0704.0267 | Cynthia S. Froning | C.S. Froning, E.L. Robinson, and M.A. Bitner | Near-Infrared Spectra of the Black Hole X-Ray Binary, A0620-00 | Accepted for publication in the Astrophysical Journal | Astrophys.J.663:1215-1224,2007 | 10.1086/518820 | null | astro-ph | null | We present broadband NIR spectra of A0620-00 obtained with SpeX on the IRTF.
The spectrum is characterized by a blue continuum on which are superimposed
broad emission lines of HI and HeII and a host of narrower absorption lines of
neutral metals and molecules. Spectral type standard star spectra scaled to the
dereddened spectrum of A0620-00 in K exceed the A0620-00 spectrum in J and H
for all stars of spectral type K7V or earlier, demonstrating that the donor
star, unless later than K7V, cannot be the sole NIR flux source in A0620-00. In
addition, the atomic absorption lines in the K3V spectrum are too weak with
respect to those of A0620-00 even at 100% donor star contribution, restricting
the spectral type of the donor star in A0620-00 to later than K3V. Comparison
of the A0620-00 spectrum to scaled K star spectra indicates that the CO
absorption features are significantly weaker in A0620-00 than in field dwarf
stars. Fits of scaled model spectra of a Roche lobe-filling donor star to the
spectrum of A0620-00 show that the best match to the CO absorption lines is
obtained when the C abundance is reduced to [C/H] = -1.5. The donor star
contribution in the H waveband is determined to be 82+-2%. Combined with
previous published results from Froning & Robinson (2001) and Marsh et al.
(1994), this gives a precise mass for the black hole in A0620-00 of M_BH =
9.7+-0.6 M_solar.
| 2009-06-23 |
0704.0268 | Mark Whitney | Mark Whitney, Nemanja Isailovic, Yatish Patel, John Kubiatowicz | Automated Generation of Layout and Control for Quantum Circuits | 16 pages, 11 figures, To appear in ACM Computing Frontiers 2007, this
version contains expanded related work | null | null | null | quant-ph | null | We present a computer-aided design flow for quantum circuits, complete with
automatic layout and control logic extraction. To motivate automated layout for
quantum circuits, we investigate grid-based layouts and show a performance
variance of four times as we vary grid structure and initial qubit placement.
We then propose two polynomial-time design heuristics: a greedy algorithm
suitable for small, congestion-free quantum circuits and a dataflow-based
analysis approach to placement and routing with implicit initial placement of
qubits. Finally, we show that our dataflow-based heuristic generates better
layouts than the state-of-the-art automated grid-based layout and scheduling
mechanism in terms of latency and potential pipelinability, but at the cost of
some area.
| 2009-09-29 |
0704.0269 | Manasvita Joshi | M. Joshi and M. Boettcher | Modeling the Spectral Energy Distribution and Variability of 3C 66A
during the WEBT campaign of 2003 -- 2004 | 23 pages, 9 figures, submitted to and accepted for publication in ApJ | Astrophys.J.662:884-891,2007 | 10.1086/518210 | null | astro-ph | null | The BL Lac object 3C 66A was observed in an extensive multiwavelength
monitoring campaign from July 2003 till April 2004. The spectral energy
distribution (SED) was measured over the entire electromagnetic spectrum, with
flux measurements from radio to X-ray frequencies and upper limits in the very
high energy (VHE) gamma-ray regime. Here, we use a time-dependent leptonic jet
model to reproduce the SED and optical spectral variability observed during our
multiwavelength campaign. Our model simulations could successfully reproduce
the observed SED and optical light curves and predict an intrinsic cutoff value
for the VHE gamma-ray emission at ~ 4 GeV. The effect of the optical depth due
to the intergalactic infrared background radiation (IIBR) on the peak of the
high-energy component of 3C 66A was found to be negligible. Also, the presence
of a broad line region (BLR) in the case of 3C 66A may play an important role
in the emission of gamma-ray photons when the emission region is very close to
the central engine, but further out, the production mechanism of hard X-ray and
gamma-ray photons becomes rapidly dominated by synchrotron self-Compton
emission. We further discuss the possibility of an observable X-ray spectral
variability pattern. The simulated results do not predict observable hysteresis
patterns in the optical or soft X-ray regimes for major flares on multi-day
time scales.
| 2009-06-23 |
0704.0270 | Xavier Bonfils | X. Bonfils, M. Mayor, X. Delfosse, T. Forveille, M. Gillon, C.
Perrier, S. Udry, F. Bouchy, C. Lovis, F. Pepe, D. Queloz, N. C. Santos and
J.-L. Bertaux | The HARPS search for southern extra-solar planets. X. A m sin i = 11
Mearth planet around the nearby spotted M dwarf GJ 674 | submitted to A&A (January 09, 2007) | null | 10.1051/0004-6361:20077068 | null | astro-ph | null | Context: How planet properties depend on stellar mass is a key diagnostic of
planetary formation mechanisms. Aims: This motivates planet searches around
stars which are significantly more massive or less massive than the Sun, and in
particular our radial velocity search for planets around very-low mass stars.
Methods: As part of that program, we obtained measurements of GJ 674, an M2.5
dwarf at d=4.5 pc, which have a dispersion much in excess of their internal
errors. An intensive observing campaign demonstrates that the excess dispersion
is due to two superimposed coherent signals, with periods of 4.69 and 35 days.
Results: These data are well described by a 2-planet Keplerian model where each
planet has a ~11 Mearth minimum mass. A careful analysis of the (low level)
magnetic activity of GJ 674 however demonstrates that the 35-day period
coincides with the stellar rotation period. This signal therefore originates in
a spot inhomogeneity modulated by stellar rotation. The 4.69-day signal on the
other hand is caused by a bona-fide planet, GJ 674b. Conclusion: Its detection
adds to the growing number of Neptune-mass planets around M-dwarfs, and
reinforces the emerging conclusion that this mass domain is much more populated
than the jovian mass range. We discuss the metallicity distributions of M dwarf
with and without planets and find a low 11% probability that they are drawn
from the same parent distribution. Moreover, we find tentative evidence that
the host star metallicity correlates with the total mass of their planetary
system.
| 2009-11-13 |
0704.0272 | Monica Ivette Rodriguez | Monica Ivette Rodriguez, Tommy Wiklind, Ronald J. Allen, Vladimir
Escalante, and Laurent Loinard | A Comparison between Anomalous 6-cm H$_2$CO Absorption and CO(1-0)
Emission in the L1204/S140 | 9 pages 6 figures ApJ:accepted | Astrophys.J.663:824-833,2007 | 10.1086/518553 | null | astro-ph | null | We report observations of the dust cloud L1204 with the Onsala 25-m telescope
in the 6 cm (1$_{11}-1_{10}$) transition of \htco. The observed region includes
the
S140 H${\alpha}$ arc. This spectral line is seen here in absorption against
the cosmic microwave background, indicating the presence of widespread warm
molecular gas at intermediate densities. Overall, the distributions of H$_2$CO
and CO (taken from the literature) are fairly similar, though significant
differences exist at small scales. Most notably, while the CO peak is nearly
coincident with the S140 H${\alpha}$ arc, the maximum H$_2$CO absorption is
clearly separated from it by a full 10$'$ beam ($\sim$ 3 pc). We argue that
these differences result from differing abundances and excitation requirements.
The CO(1-0) line is more optically thick and more biased towards warm gas than
the H$_2$CO 6 cm line. On the other hand, formaldehyde is more easily
photodissociated and is, therefore, a poorer tracer of the molecular gas
located immediately behind Photon Dominated Regions.
| 2009-06-23 |
0704.0276 | Maik Wolleben | M. Wolleben | A New Model For The Loop-I (The North Polar Spur) Region | 17 pages, 6 figures, to appear in ApJ | Astrophys.J.664:349-356,2007 | 10.1086/518711 | null | astro-ph | null | The North Polar Spur (NPS) is the brightest filament of Loop I, a large
circular feature in the radio continuum sky. In this paper, a model consisting
of two synchrotron emitting shells is presented that reproduces large-scale
structures revealed by recent polarization surveys. The polarized emission of
the NPS is reproduced by one of these shells. The other shell, which passes
close to the Sun, gives rise to polarized emission towards the Galactic poles.
It is proposed that X-ray emission seen towards the NPS is produced by
interaction of the two shells. Two OB-associations coincide with the centers of
the shells. A formation scenario of the Loop I region is suggested.
| 2009-06-23 |
0704.0279 | Andreea O. Petric | A. O. Petric and M. P. Rupen | HI velocity dispersion in NGC 1058 | 29 pages, 16 figures reduced to the lowest qual. to fit the astro-ph
size requirements, accepted by AJ | Astron.J.134:1952-1962,2007 | 10.1086/518558 | null | astro-ph | null | We present excellent resolution and high sensitivity Very Large Array (VLA)
observations of the 21cm HI line emission from the face-on galaxy NGC 1058,
providing the first reliable study of the HI profile shapes throughout the
entire disk of an external galaxy. Our observations show an intriguing picture
of the interstellar medium; throughout this galaxy velocity-- dispersions range
between 4 to 15 km/sec but are not correlated with star formation, stars or the
gaseous spiral arms. The velocity dispersions decrease with radius, but this
global trend has a large scatter as there are several isolated, resolved
regions of high dispersion. The decline of star light with radius is much
steeper than that of the velocity dispersions or that of the energy in the gas
motions.
| 2009-06-23 |
0704.0280 | Ronald F. Webbink | Ronald F. Webbink (University of Illinois at Urbana-Champaign) | Common Envelope Evolution Redux | 25 pages, 6 figures. To appear in "Short Period Binary Stars", ed.
E.F. Milone, D.A. Leahy, & D.W. Hobill (Springer) | null | 10.1007/978-1-4020-6544-6_13 | null | astro-ph | null | Common envelopes form in dynamical time scale mass exchange, when the
envelope of a donor star engulfs a much denser companion, and the core of the
donor plus the dense companion star spiral inward through this dissipative
envelope. As conceived by Paczynski and Ostriker, this process must be
responsible for the creation of short-period binaries with degenerate
components, and, indeed, it has proven capable of accounting for short-period
binaries containing one white dwarf component. However, attempts to reconstruct
the evolutionary histories of close double white dwarfs have proven more
problematic, and point to the need for enhanced systemic mass loss, either
during the close of the first, slow episode of mass transfer that produced the
first white dwarf, or during the detached phase preceding the final, common
envelope episode. The survival of long-period interacting binaries with massive
white dwarfs, such as the recurrent novae T CrB and RS Oph, also presents
interpretative difficulties for simple energetic treatments of common envelope
evolution. Their existence implies that major terms are missing from usual
formulations of the energy budget for common envelope evolution. The most
plausible missing energy term is the energy released by recombination in the
common envelope, and, indeed, a simple reformulation the energy budget
explicitly including recombination resolves this issue.
| 2015-11-11 |
0704.0281 | Denis Richard | Denis Richard | The Source of Turbulence in Astrophysical Disks: An Ill-posed Problem. | UCSC-NASA Ames Research Center Workshop on Stellar and Planets
Formation March 29, 2007 | null | null | null | astro-ph | null | An critical overview of the current state of research in turbulence in
astrophysical disks.
| 2007-05-23 |
0704.0287 | Pablo M. Saz Parkinson | Pablo M. Saz Parkinson (Milagro Collaboration) | Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro | To appear in "Proceedings of the First International GLAST
Symposium", Febuary 5-8, 2007, Stanford University, AIP, Eds. S. Ritz, P. F.
Michelson, and C. Meegan | null | 10.1063/1.2757406 | null | astro-ph | null | Gamma-Ray Bursts (GRBs) have been detected at GeV energies by EGRET and
models predict emission at > 100 GeV. Milagro is a wide field (2 sr) high duty
cycle (> 90 %) ground based water Cherenkov detector that records extensive air
showers in the energy range 100 GeV to 100 TeV. We have searched for very high
energy emission from a sample of 106 gamma-ray bursts (GRB) detected since the
beginning of 2000 by BATSE, BeppoSax, HETE-2, INTEGRAL, Swift or the IPN. No
evidence for emission from any of the bursts has been found and we present
upper limits from these bursts.
| 2009-11-13 |
0704.0290 | Jarrod R. Hurley | Jarrod R. Hurley, Sverre J. Aarseth, Michael M. Shara | The core binary fractions of star clusters from realistic simulations | 34 pages, 12 figures, accepted for publication in the Astrophysical
Journal | Astrophys.J.665:707-718,2007 | 10.1086/517879 | null | astro-ph | null | We investigate the evolution of binary fractions in star clusters using
N-body models of up to 100000 stars. Primordial binary frequencies in these
models range from 5% to 50%. Simulations are performed with the NBODY4 code and
include a full mass spectrum of stars, stellar evolution, binary evolution and
the tidal field of the Galaxy. We find that the overall binary fraction of a
cluster almost always remains close to the primordial value, except at late
times when a cluster is near dissolution. A critical exception occurs in the
central regions where we observe a marked increase in binary fraction with time
-- a simulation starting with 100000 stars and 5% binaries reached a core
binary frequency as high as 40% at the end of the core-collapse phase
(occurring at 16 Gyr with ~20000 stars remaining). Binaries are destroyed in
the core by a variety of processes as a cluster evolves, but the combination of
mass-segregation and creation of new binaries in exchange interactions produces
the observed increase in relative number. We also find that binaries are cycled
into and out of cluster cores in a manner that is analogous to convection in
stars. For models of 100000 stars we show that the evolution of the core-radius
up to the end of the initial phase of core-collapse is not affected by the
exact value of the primordial binary frequency (for frequencies of 10% or
less). We discuss the ramifications of our results for the likely primordial
binary content of globular clusters.
| 2009-06-23 |
0704.0292 | Gregory Soyez | Gavin P. Salam and Gregory Soyez | A practical Seedless Infrared-Safe Cone jet algorithm | 42 pages, 11 figures. SISCone, the C++ implementation of the
algorithm, is available at http://projects.hepforge.org/siscone/
(standalone), http://www.lpthe.jussieu.fr/~salam/fastjet/ (FastJet plugin).
v2: FastJet URL corrected | JHEP 0705:086,2007 | 10.1088/1126-6708/2007/05/086 | null | hep-ph | null | Current cone jet algorithms, widely used at hadron colliders, take event
particles as seeds in an iterative search for stable cones. A longstanding
infrared (IR) unsafety issue in such algorithms is often assumed to be solvable
by adding extra `midpoint' seeds, but actually is just postponed to one order
higher in the coupling. A proper solution is to switch to an exact seedless
cone algorithm, one that provably identifies all stable cones. The only
existing approach takes N 2^N time to find jets among N particles, making it
unusable at hadron level. This can be reduced to N^2 ln(N) time, leading to
code (SISCone) whose speed is similar to that of public midpoint
implementations. Monte Carlo tests provide a strong cross-check of an
analytical proof of the IR safety of the new algorithm, and the absence of any
'R_{sep}' issue implies a good practical correspondence between parton and
hadron levels. Relative to a midpoint cone, the use of an IR safe seedless
algorithm leads to modest changes for inclusive jet spectra, mostly through
reduced sensitivity to the underlying event, and significant changes for some
multi-jet observables.
| 2009-11-13 |
0704.0293 | Mikhail Voloshin | S. Dubynskiy, A. Le Yaouanc, L. Oliver, J.-C. Raynal and M.B. Voloshin | Isospin breaking in the yield of heavy meson pairs in e+e- annihilation
near threshold | 16 pages, 2 figures | Phys.Rev.D75:113001,2007 | 10.1103/PhysRevD.75.113001 | FTPI-MINN-07/08, UMN-TH-2541/07, LPT-Orsay/07-19 | hep-ph | null | We revisit the problem of interplay between the strong and the Coulomb
interaction in the charged-to-neutral yield ratio for $B {\bar B}$ and $D {\bar
D}$ pairs near their respective thresholds in $e^+e^-$ annihilation. We
consider here a realistic situation with a resonant interaction in the isospin
I=0 channel and a nonresonant strong scattering amplitude in the I=1 state. We
find that the yield ratio has a smooth behavior depending on the scattering
phase in the I=1 channel. The same approach is also applicable to the $K {\bar
K}$ production at the $\phi(1020)$ resonance, where the Coulomb effect in the
charged-to-neutral yield ratio is generally sensitive to the scattering phases
in both the isoscalar and the isovector channels. Furthermore, we apply the
same approach to the treatment of the effect of the isotopic mass difference
between the charged and neutral mesons and argue that the strong-scattering
effects generally result in a modification to the pure kinematical effect of
this mass difference.
| 2008-11-26 |
0704.0294 | Scott A. Yost | B.F.L. Ward and S.A. Yost | QED x QCD Resummation and Shower/ME Matching for LHC Physics | 12 pages, LaTex with packages amsmath, amssymb | ActaPhys.Polon.B38:2395-2403,2007 | null | BU-HEPP-07/02 | hep-ph | null | We present the theory of QED x QCD resummation and its interplay with
shower/matrix element matching in precision LHC physics scenarios. We
illustrate the theory using single heavy gauge boson production at hadron
colliders.
| 2008-11-26 |
0704.0296 | Itzhak Bars | Itzhak Bars and Bora Orcal | Generalized Twistor Transform And Dualities, With A New Description of
Particles With Spin, Beyond Free and Massless | 33 pages | Phys.Rev.D75:104015,2007 | 10.1103/PhysRevD.75.104015 | USC-07/HEP-B3 | hep-th | null | A generalized twistor transform for spinning particles in 3+1 dimensions is
constructed that beautifully unifies many types of spinning systems by mapping
them to the same twistor, thus predicting an infinite set of duality relations
among spinning systems with different Hamiltonians. Usual 1T-physics is not
equipped to explain the duality relationships and unification between these
systems. We use 2T-physics in 4+2 dimensions to uncover new properties of
twistors, and expect that our approach will prove to be useful for practical
applications as well as for a deeper understanding of fundamental physics.
Unexpected structures for a new description of spinning particles emerge. A
unifying symmetry SU(2,3) that includes conformal symmetry SU(2,2)=SO(4,2) in
the massless case, turns out to be a fundamental property underlying the
dualities of a large set of spinning systems, including those that occur in
high spin theories. This may lead to new forms of string theory backgrounds as
well as to new methods for studying various corners of M theory. In this paper
we present the main concepts, and in a companion paper we give other details.
| 2008-11-26 |
0704.0297 | Sung-Chul Yoon | Sung-Chul Yoon, Philipp Podsiadlowski and Stephan Rosswog | Remnant evolution after a carbon-oxygen white dwarf merger | 15 pages, 15 figures, 3 tables, submitted to MNRAS (Low resolution
version; a high resolution version can be found at:
http://www.astro.uva.nl/~scyoon/papers/wdmerger.pdf) | null | 10.1111/j.1365-2966.2007.12161.x | null | astro-ph | null | We systematically explore the evolution of the merger of two carbon-oxygen
(CO) white dwarfs. The dynamical evolution of a 0.9 Msun + 0.6 Msun CO white
dwarf merger is followed by a three-dimensional SPH simulation. We use an
elaborate prescription in which artificial viscosity is essentially absent,
unless a shock is detected, and a much larger number of SPH particles than
earlier calculations. Based on this simulation, we suggest that the central
region of the merger remnant can, once it has reached quasi-static equilibrium,
be approximated as a differentially rotating CO star, which consists of a
slowly rotating cold core and a rapidly rotating hot envelope surrounded by a
centrifugally supported disc. We construct a model of the CO remnant that
mimics the results of the SPH simulation using a one-dimensional hydrodynamic
stellar evolution code and then follow its secular evolution. The stellar
evolution models indicate that the growth of the cold core is controlled by
neutrino cooling at the interface between the core and the hot envelope, and
that carbon ignition in the envelope can be avoided despite high effective
accretion rates. This result suggests that the assumption of forced accretion
of cold matter that was adopted in previous studies of the evolution of double
CO white dwarf merger remnants may not be appropriate. Our results imply that
at least some products of double CO white dwarfs merger may be considered good
candidates for the progenitors of Type Ia supernovae. In this case, the
characteristic time delay between the initial dynamical merger and the eventual
explosion would be ~10^5 yr. (Abridged).
| 2019-08-19 |
0704.0307 | Eric L. N. Jensen | Eric L. N. Jensen (1), Saurav Dhital (1,2), Keivan G. Stassun (2),
Jenny Patience (3), William Herbst (4), Frederick M. Walter (5), Michal Simon
(5), Gibor Basri (6); (1 - Swarthmore College; 2 - Vanderbilt; 3 - Caltech; 4
- Wesleyan University; 5 - SUNY Stony Brook; 6 - UC Berkeley) | Periodic accretion from a circumbinary disk in the young binary UZ Tau E | Accepted by the Astronomical Journal; to appear July 2007; Corrected
minor typos | Astron.J.134:241-251,2007 | 10.1086/518408 | null | astro-ph | null | Close pre-main-sequence binary stars are expected to clear central holes in
their protoplanetary disks, but the extent to which material can flow from the
circumbinary disk across the gap onto the individual circumstellar disks has
been unclear. In binaries with eccentric orbits, periodic perturbation of the
outer disk is predicted to induce mass flow across the gap, resulting in
accretion that varies with the binary period. This accretion may manifest
itself observationally as periodic changes in luminosity. Here we present a
search for such periodic accretion in the pre-main-sequence spectroscopic
binary UZ Tau E. We present BVRI photometry spanning three years; we find that
the brightness of UZ Tau E is clearly periodic, with a best-fit period of 19.16
+/- 0.04 days. This is consistent with the spectroscopic binary period of 19.13
days, refined here from analysis of new and existing radial velocity data. The
brightness of UZ Tau E shows significant random variability, but the overall
periodic pattern is a broad peak in enhanced brightness, spanning more than
half the binary orbital period. The variability of the H-alpha line is not as
clearly periodic, but given the sparseness of the data, some periodic component
is not ruled out. The photometric variations are in good agreement with
predictions from simulations of binaries with orbital parameters similar to
those of UZ Tau E, suggesting that periodic accretion does occur from
circumbinary disks, replenishing the inner disks and possibly extending the
timescale over which they might form planets.
| 2009-06-23 |
0704.0310 | Xiang Liu | Xiang Liu, Lang Cui, Wen-Feng Luo, Wei-Zhao Shi, Hua-Gang Song (Urumqi
Observatory, NAOC) | VLBI observations of nineteen GHz-Peaked-Spectrum radio sources at 1.6
GHz | 11 pages, 12 figures, to appear in AA | A&A 470, 97-104 (2007) | 10.1051/0004-6361:20077265 | null | astro-ph | null | Aims and Methods: We present the results of VLBI observations of nineteen
GHz-Peaked-Spectrum (GPS) radio sources at 1.6 GHz. Of them, 15 sources are
selected from the Parkes Half Jansky (PHJ) sample (Snellen 2002), 4 others are
from our previous observation list. We aimed at imaging the structure of GPS
sources, searching for Compact Symmetric Objects (CSOs) and studying the
absorption for the convex radio spectra of GPS sources.
Results: We obtained total intensity 1.6 GHz VLBI images of 17 sources for
the first time. Of them, 80% show mini-double-lobe radio structure, indicating
that they are CSOs or candidates, and their host AGNs could be edge-on to us.
This result suggests that there is a high incidence of mini double-lobe sources
(or CSOs) in the PHJ sample. The sources J0323+0534, J1135-0021, J1352+0232,
J2058+0540, J2123-0112 and J2325-0344 with measured redshift, showing
double-lobe structure with sizes of <1 kpc, are classified as CSOs. Three
sources J1057+0012, J1600-0037 and J1753+2750 are considered as core-jet
sources according to their morphologies and flux variability.
| 2007-07-10 |
0704.0312 | Geraint F. Lewis | Matthew J. Francis, Geraint F. Lewis, Eric V. Linder | Power Spectra to 1% Accuracy between Dynamical Dark Energy Cosmologies | 9 pages, 14 figures, submitted to MNRAS | Mon.Not.Roy.Astron.Soc.380:1079,2007 | 10.1111/j.1365-2966.2007.12139.x | GFL-001 | astro-ph | null | For dynamical dark energy cosmologies we carry out a series of N-body
gravitational simulations, achieving percent level accuracy in the relative
mass power spectra at any redshift. Such accuracy in the power spectrum is
necessary for next generation cosmological mass probes. Our matching procedure
reproduces the CMB distance to last scattering and delivers subpercent level
power spectra at z=0 and z~3. We discuss the physical implications for probing
dark energy with surveys of large scale structure.
| 2009-06-23 |
0704.0316 | Alister W. Graham | Alister W. Graham, Simon P. Driver, Paul D. Allen, Jochen Liske | The Millennium Galaxy Catalogue: The local supermassive black hole mass
function in early- and late-type galaxies | 10 pages of text plus 5 of figs and refs. MNRAS, accepted. | Mon.Not.Roy.Astron.Soc.378:198-210,2007 | 10.1111/j.1365-2966.2007.11770.x | null | astro-ph | null | We provide a new estimate of the local supermassive black hole mass function
using (i) the empirical relation between supermassive black hole mass and the
Sersic index of the host spheroidal stellar system and (ii) the measured
(spheroid) Sersic indices drawn from 10k galaxies in the Millennium Galaxy
Catalogue. The observational simplicity of our approach, and the direct
measurements of the black hole predictor quantity, i.e. the Sersic index, for
both elliptical galaxies and the bulges of disc galaxies makes it
straightforward to estimate accurate black hole masses in early- and late-type
galaxies alike. We have parameterised the supermassive black hole mass function
with a Schechter function and find, at the low-mass end, a logarithmic slope
(1+alpha) of ~0.7 for the full galaxy sample and ~1.0 for the early-type galaxy
sample. Considering spheroidal stellar systems brighter than M_B = -18 mag, and
integrating down to black hole masses of 10^6 M_sun, we find that the local
mass density of supermassive black holes in early-type galaxies rho_{bh,
early-type} = (3.5+/-1.2) x 10^5 h^3_{70} M_sun Mpc^{-3}, and in late-type
galaxies rho_{bh, late-type} = (1.0+/-0.5) x 10^5 h^3_{70} M_sun Mpc^{-3}. The
uncertainties are derived from Monte Carlo simulations which include
uncertainties in the M_bh-n relation, the catalogue of Sersic indices, the
galaxy weights and Malmquist bias. The combined, cosmological, supermassive
black hole mass density is thus Omega_{bh, total} = (3.2+/-1.2) x 10^{-6} h_70.
That is, using a new and independent method, we conclude that (0.007+/-0.003)
h^3_{70} per cent of the universe's baryons are presently locked up in
supermassive black holes at the centres of galaxies.
| 2012-04-26 |
0704.0323 | Heng Fan | Gui-Fang Dang, and Heng Fan | General sequential quantum cloning | 4 pages | J.Phys.A 41, 155303 (2008) | 10.1088/1751-8113/41/15/155303 | null | quant-ph | null | Some multipartite quantum states can be generated in a sequential manner
which may be implemented by various physical setups like microwave and optical
cavity QED, trapped ions, and quantum dots etc. We analyze the general N to M
qubits Universal Quantum Cloning Machine (UQCM) within a sequential generation
scheme. We show that the N to M sequential UQCM is available. The case of
d-level quantum states sequential cloning is also presented.
| 2012-05-23 |
0704.0328 | Seung Woo Ham | S.W. Ham, E.J. Yoo, S.K. OH | Electroweak phase transitions in the MSSM with an extra $U(1)'$ | 17 pages, 2 tables, 3 figures | Phys.Rev.D76:075011,2007 | 10.1103/PhysRevD.76.075011 | null | hep-ph | null | We investigate the possibility of electroweak phase transition in the minimal
supersymmetric standard model (MSSM) with an extra $U(1)'$. This model has two
Higgs doublets and a singlet, in addition to a singlet exotic quark superfield.
We find that at the one-loop level this model may accommodate the electroweak
phase transitions that are strongly first-order in a reasonably large region of
the parameter space. In the parameter region where the phase transitions take
place, we observe that the lightest scalar Higgs boson has a smaller mass when
the strength of the phase transition becomes weaker. Also, the other three
heavier neutral Higgs bosons get more large masses when the strength of the
phase transition becomes weaker.
| 2008-11-26 |
0704.0330 | Jacobus Verbaarschot | K. Splittorff and J.J.M. Verbaarschot | Random Matrix Theory at Nonzero $\mu$ and $T$ | Invited talk at YKIS2006, YITP-Kyoto, 10 pages, 10 figures | Prog.Theor.Phys.Suppl.168:265-275,2007 | 10.1143/PTPS.168.265 | null | hep-ph | null | We review applications of random matrix theory to QCD at nonzero temperature
and chemical potential. The chiral phase transition of QCD and QCD-like
theories is discussed in terms of eigenvalues of the Dirac operator. We show
that for QCD at $\mu \ne 0$, which has a sign problem, the discontinuity in the
chiral condensate is due to an alternative to the Banks-Casher relation. The
severity of the sign problem is analyzed in the microscopic domain of QCD.
| 2008-11-26 |
0704.0340 | Fam Le Kien | Fam Le Kien, S. Dutta Gupta, and K. Hakuta | Phonon-mediated decay of an atom in a surface-induced potential | 14 pages, 15 figures | null | null | null | quant-ph | null | We study phonon-mediated transitions between translational levels of an atom
in a surface-induced potential. We present a general master equation governing
the dynamics of the translational states of the atom. In the framework of the
Debye model, we derive compact expressions for the rates for both upward and
downward transitions. Numerical calculations for the transition rates are
performed for a deep silica-induced potential allowing for a large number of
bound levels as well as free states of a cesium atom. The total absorption rate
is shown to be determined mainly by the bound-to-bound transitions for deep
bound levels and by bound-to-free transitions for shallow bound levels.
Moreover, the phonon emission and absorption processes can be orders of
magnitude larger for deep bound levels as compared to the shallow bound ones.
We also study various types of transitions from free states. We show that, for
thermal atomic cesium with temperature in the range from 100 $\mu$K to 400
$\mu$K in the vicinity of a silica surface with temperature of 300 K, the
adsorption (free-to-bound decay) rate is about two times larger than the
heating (free-to-free upward decay) rate, while the cooling (free-to-free
downward decay) rate is negligible.
| 2007-05-23 |
0704.0341 | Boris Ermolaev | B.I. Ermolaev, M. Greco, S.I. Troyan | Infrared Evolution Equations: Method and Applications | Talk given at Cracow Epiphany conference on precision physics and
Monte Carlos for LHS. 4-6 January 2007, Cracow, Poland. 12 pp, 3 figures. | Acta Phys.Polon.B38:2243-2260,2007 | null | null | hep-ph | null | It is a brief review on composing and solving Infrared Evolution Equations.
They can be used in order to calculate amplitudes of high-energy reactions in
different kinematic regions in the double-logarithmic approximation.
| 2011-04-11 |
0704.0344 | Fabrizio Tavecchio | L. Maraschi, G. Ghisellini, F. Tavecchio | The Blazar Spectral Sequence and GLAST | 3 pages, 4 figures. Proceedings of the First GLAST Symposium, to be
published | AIP Conf.Proc.921:160-162,2007 | 10.1063/1.2757292 | null | astro-ph | null | The present status and understanding of the "spectral sequence" of blazars is
discussed in the perspective of the upcoming GLAST launch. The vast improvement
in sensitivity will allow to i) determine more objectively the "average"
gamma-ray properties of classes objects ii) probe more deeply the ratio between
accretion power and jet power in different systems.
| 2009-06-23 |
0704.0346 | Kenji Hamaguchi | Kenji Hamaguchi, the Suzaku Eta Carinae team and the Carinae D-1 team | Diffuse X-ray Emission from the Carina Nebula Observed with Suzaku | 4 pages, 2 figures, proceeding of the extreme universe in the Suzaku
era, held in Kyoto, Japan on Dec. 4-8, 2006 | null | 10.1143/PTPS.169.174 | null | astro-ph | null | A number of giant HII regions are associated with soft diffuse X-ray
emission. Among these, the Carina nebula possesses the brightest soft diffuse
emission. The required plasma temperature and thermal energy can be produced by
collisions or termination of fast winds from main-sequence or embedded young O
stars, but the extended emission is often observed from regions apart from
massive stellar clusters. The origin of the X-ray emission is unknown.
The XIS CCD camera onboard Suzaku has the best spectral resolution for
extended soft sources so far, and is therefore capable of measuring key
emission lines in the soft band. Suzaku observed the core and the eastern side
of the Carina nebula (Car-D1) in 2005 Aug and 2006 June, respectively. Spectra
of the south part of the core and Car-D1 similarly showed strong L-shell lines
of iron ions and K-shell lines of silicon ions, while in the north of the core
these lines were much weaker. Fitting the spectra with an absorbed thin-thermal
plasma model showed kT~0.2, 0.6 keV and NH~1-2e21 cm-2 with a factor of 2-3
abundance variation in oxygen, magnesium, silicon and iron. The plasma might
originate from an old supernova, or a super shell of multiple supernovae.
| 2009-11-13 |
0704.0348 | Grazyna Stasinska | G. Stasinska | What can emission lines tell us? | 55 pages, Lectures given at the XVIII Canary Island Winterschool "The
emission line Universe", to be published by Cambridge University Press | null | 10.1017/CBO9780511552038.003 | null | astro-ph | null | 1 Generalities
2 Empirical diagnostics based on emission lines
3 Photoionization modelling
4 Pending questions
5 Appendix: Lists of useful lines and how to deal with them
| 2023-06-07 |
0704.0350 | Sonia Fornasier | S. Fornasier, E. Dotto, O. Hainaut, F. Marzari, H. Boehnhardt, F. De
Luise, M. A. Barucci | Visible spectroscopic and photometric survey of Jupiter Trojans: final
results on dynamical families | 52 pages, 14 figure, paper accepted for publication in Icarus | null | 10.1016/j.icarus.2007.03.033 | null | astro-ph | null | We present the results of a visible spectroscopic and photometric survey of
Jupiter Trojans belonging to different dynamical families carried out at the
ESO-NTT telescope. We obtained data on 47 objects, 23 belonging to the L5 swarm
and 24 to the L4 one. These data together with those already published by
Fornasier et al. (2004a) and Dotto et al. (2006), constitute a total sample of
visible spectra for 80 objects. The survey allows us to investigate six
families (Aneas, Anchises, Misenus, Phereclos, Sarpedon, Panthoos) in the L5
cloud and four L4 families (Eurybates, Menelaus, 1986 WD and 1986 TS6). The
sample that we measured is dominated by D--type asteroids, with the exception
of the Eurybates family in the L4 swarm, where there is a dominance of C- and
P-type asteroids. All the spectra that we obtained are featureless with the
exception of some Eurybates members, where a drop--off of the reflectance is
detected shortward of 5200 A. Similar features are seen in main belt C-type
asteroids and commonly attributed to the intervalence charge transfer
transition in oxidized iron. Our sample comprises fainter and smaller Trojans
as compared to the literature's data and allows us to investigate the
properties of objects with estimated diameter smaller than 40--50 km. The
analysis of the spectral slopes and colors versus the estimated diameters shows
that the blue and red objects have indistinguishable size distribution. We
perform a statistical investigation of the Trojans's spectra property
distributions as a function of their orbital and physical parameters, and in
comparison with other classes of minor bodies in the outer Solar System.
Trojans at lower inclination appear significantly bluer than those at higher
inclination, but this effect is strongly driven by the Eurybates family.
| 2009-11-13 |
End of preview. Expand
in Dataset Viewer.
- Downloads last month
- 37