5,836 research outputs found
Optimality Inequalities for Average Cost Markov Decision Processes and the Optimality of (s,S) Policies
Optimality Inequalities for Average Cost Markov Decision Processes and the Optimality of (s,S) Policie
Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath
We explore the consequences of Bose-Einstein condensation on
two-scalar-exchange mediated forces among bodies that sit in a boson gas. We
find that below the condensation temperature the range of the forces becomes
infinite while it is finite at temperatures above condensation.Comment: 10 pages, 2 figure
Programmable telemetry system Patent
Time division multiplexed telemetry transmitting system controlled by programmed memor
Constraints on Light Pseudoscalars Implied by Tests of the Gravitational Inverse-Square Law
The exchange of light pseudoscalars between fermions leads to a
spin-independent potential in order g^4, where g is the Yukawa
pseudoscalar-fermion coupling constant. This potential gives rise to detectable
violations of both the weak equivalence principle (WEP) and the gravitational
inverse-square law (ISL), even if g is quite small. We show that when
previously derived WEP constraints are combined with those arisingfrom ISL
tests, a direct experimental limit on the Yukawa coupling of light
pseudoscalars to neutrons can be inferred for the first time (g_n^2/4pi < 1.6
\times 10^-7), along with a new (and significantly improved) limit on the
coupling of light pseudoscalars to protons.Comment: 12 pages, Revtex, with 1 Postscript figure (submitted to Physical
Review Letters
Long Range Forces from Pseudoscalar Exchange
Using dispersion theoretic techniques, we consider coherent long range forces
arising from double pseudoscalar exchange among fermions. We find that Yukawa
type coupling leads to spin independent attractive potentials whereas
derivative coupling renders spin independent repulsive potentials.Comment: 27 pages, REVTeX, 3 figures included using epsfi
Analysis of dilepton production in Au+Au collisions at sqrt(s_NN)=200 GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach
We address dilepton production in Au+Au collisions at sqrt(s_NN)=200 GeV by
employing the parton-hadron-string dynamics (PHSD) off-shell transport
approach. Within the PHSD one goes beyond the quasiparticle approximation by
solving generalized transport equations on the basis of the off-shell
Kadanoff-Baym equations for the Green's functions in the phase-space
representation. The approach consistently describes the full evolution of a
relativistic heavy-ion collision from the initial hard scatterings and string
formation through the dynamical deconfinement phase transition to the
quark-gluon plasma (QGP) as well as hadronization and to the subsequent
interactions in the hadronic phase. {With partons described in the PHSD by the
dynamical quasiparticle model (DQPM) - matched to reproduce lattice QCD results
in thermodynamic equilibrium} - we calculate, in particular, the dilepton
radiation from partonic interactions through the reactions q+qbar->gamma^*,
q+qbar->gamma^*+g and q+g->gamma^*+q (qbar+g->gamma^*+qbar) in the early stage
of relativistic heavy-ion collisions. By comparing our results to the data from
the PHENIX Collaboration, we study the relative importance of different
dilepton production mechanisms and point out the regions in phase space where
partonic channels are dominant. Furthermore, explicit predictions are presented
for dileptons within the acceptance of the STAR detector system and compared to
the preliminary data.Comment: 11 pages, 10 figures. arXiv admin note: substantial text overlap with
arXiv:1107.340
Scaling and Universality of the Complexity of Analog Computation
We apply a probabilistic approach to study the computational complexity of
analog computers which solve linear programming problems. We analyze
numerically various ensembles of linear programming problems and obtain, for
each of these ensembles, the probability distribution functions of certain
quantities which measure the computational complexity, known as the convergence
rate, the barrier and the computation time. We find that in the limit of very
large problems these probability distributions are universal scaling functions.
In other words, the probability distribution function for each of these three
quantities becomes, in the limit of large problem size, a function of a single
scaling variable, which is a certain composition of the quantity in question
and the size of the system. Moreover, various ensembles studied seem to lead
essentially to the same scaling functions, which depend only on the variance of
the ensemble. These results extend analytical and numerical results obtained
recently for the Gaussian ensemble, and support the conjecture that these
scaling functions are universal.Comment: 22 pages, latex, 12 eps fig
Initial correlations effects on decoherence at zero temperature
We consider a free charged particle interacting with an electromagnetic bath
at zero temperature. The dipole approximation is used to treat the bath
wavelengths larger than the width of the particle wave packet. The effect of
these wavelengths is described then by a linear Hamiltonian whose form is
analogous to phenomenological Hamiltonians previously adopted to describe the
free particle-bath interaction. We study how the time dependence of decoherence
evolution is related with initial particle-bath correlations. We show that
decoherence is related to the time dependent dressing of the particle. Moreover
because decoherence induced by the T=0 bath is very rapid, we make some
considerations on the conditions under which interference may be experimentally
observed.Comment: 16 pages, 1 figur
Effective Non-Hermitian Hamiltonians for Studying Resonance Statistics in Open Disordered Systems
We briefly discuss construction of energy-dependent effective non-hermitian
hamiltonians for studying resonances in open disordered systemsComment: Latex, 20 pages, 1 fig. Expanded version of a talk at the Workshop on
Pseudo-Hermitian Hamiltonians in Quantum Physics IX, June 21-24 2010,
Zhejiang University, Hangzhou, China. Accepted for publication in the
Internationa Journal of Theoretical Physics (Springer Verlag
Elastic precession of electronic spin states in interacting integer quantum Hall edge channels
We consider the effect of Coulomb interactions in the propagation of
electrons, prepared in arbitrary spin states, on chiral edge channels in the
integer quantum Hall regime. Electrons are injected and detected at the same
energy at different locations of the Hall bar, which is modeled as a chiral
Tomonaga-Luttinger liquid. The current is computed perturbatively in the
tunneling amplitudes, within a non-crossing approximation using exact solutions
of the interacting Green's functions. In the case of different channel
velocities, the spin precession effect is evaluated, and the role of
interaction parameters and wavevectors is discussed.Comment: 5 pages, 3 figure
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