46,958 research outputs found
A web-tool for population synthesis of near-by cooling neutron stars: An on-line test for cooling curves
We present a new web-tool - Net-PSICoNS - for population synthesis of
isolated near-by cooling neutron stars (NSs). The main aim is to provide an
easy test of models of the NS thermal evolution which can be used by groups
studying this subject. A user can upload cooling curves for a set of masses,
modify the mass spectrum if necessary, change radii to fit the EoS used for
cooling curve calculations, and then a population synthesis of close-by
isolated cooling NSs is performed. The output includes the Log N -- Log S
distribution confronted with the ROSAT observations and several other sets of
data. In this paper, we summarize the idea of the test proposed by Popov et al.
(2006), and present a user's manual for the web-tool.Comment: 6 pages, accepted to A
Holomorphic Analogs of Topological Gauge Theories
We introduce a new class of gauge field theories in any complex dimension,
based on algebra-valued (p,q)-forms on complex n-manifolds. These theories are
holomorphic analogs of the well-known Chern-Simons and BF topological theories
defined on real manifolds. We introduce actions for different special
holomorphic BF theories on complex, Kahler and Calabi-Yau manifolds and
describe their gauge symmetries. Candidate observables, topological invariants
and relations to integrable models are briefly discussed.Comment: 12 pages, LaTeX2e, shortened PLB versio
Symmetries in nonlinear Bethe-Heitler process
Nonlinear Bethe-Heitler process in a bichromatic laser field is investigated
using strong-field QED formalism. Symmetry properties of angular distributions
of created pairs are analyzed. These properties are showed to be
governed by a behavior of the vector potential characterizing the laser field,
rather than by the respective electric field component.Comment: 4 pages, 4 figure
Towards laser based improved experimental schemes for multiphoton e+ e- pair production from vacuum
Numerical estimates for pair production from vacuum in the presence of strong
electromagnetic fields are derived, for two experimental schemes : the First
concerns a laser based X-FEL and the other imitates the E144 experiment. The
approximation adopted in this work is that of two level multiphoton on
resonance. Utilizing achievable values of laser beam parameters, an
enhancedproduction efficiency of up to 10^11 and 10^15 pairs can be obtained,
for the two schemes respectively.Comment: 6 pages, 4 figure
Closed N=2 Strings: Picture-Changing, Hidden Symmetries and SDG Hierarchy
We study the action of picture-changing and spectral flow operators on a
ground ring of ghost number zero operators in the chiral BRST cohomology of the
closed N=2 string and describe an infinite set of symmetry charges acting on
physical states. The transformations of physical string states are compared
with symmetries of self-dual gravity which is the effective field theory of the
closed N=2 string. We derive all infinitesimal symmetries of the self-dual
gravity equations in 2+2 dimensional spacetime and introduce an infinite
hierarchy of commuting flows on the moduli space of self-dual metrics. The
dependence on moduli parameters can be recovered by solving the equations of
the SDG hierarchy associated with an infinite set of abelian symmetries
generated recursively from translations. These non-local abelian symmetries are
shown to coincide with the hidden abelian string symmetries responsible for the
vanishing of most scattering amplitudes. Therefore, N=2 string theory
"predicts" not only self-dual gravity but also the SDG hierarchy.Comment: 41 pages, no figure
Measurements of single top-quark production in pp collisions by the CMS experiment
A summary of studies of electroweak top-quark production performed by the CMS
collaboration is presented. The results include measurements of production
cross sections, extraction of the value of , determination of W-boson
helicity in top-quark decays and top-quark spin asymmetry, and a search for
anomalous couplings in the Wtb vertex. No deviations from predictions of the
standard model are found.Comment: Proceedings of the 8th International Workshop on the CKM Unitarity
Triangle (CKM 2014), Vienna, Austria, September 8-12, 201
On a scale-invariant Fermi gas in a time-dependent harmonic potential
We investigate a scale-invariant two-component Fermi gas in a time-dependent
isotropic harmonic potential. The exact time evolution of the density
distribution in position space in any spatial dimension is obtained. Two
experimentally relevant examples, an abrupt change and a periodic modulation of
the trapping frequency are solved. Small deviations from scale invariance and
isotropy of the confinement are addressed within first order perturbation
theory. We discuss the consequences for experiments with ultracold quantum
gases such as the excitation of a tower of undamped breathing modes and a new
alternative for measuring the Tan contact.Comment: 6+3 pages, 2 figures; revised and extended versio
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