1,393,220 research outputs found
critRHIC: The RHIC Low Energy Program
Recent experimental and theoretical developments have motivated interest in a
more detailed exploration of heavy ion collisions in the range sqrt(sNN)=5-15
GeV. In contrast to interactions at the full RHIC energy of sqrt(sNN)=200 GeV,
such collisions result in systems characterized by much higher baryon chemical
potential, muB. Extensions of lattice QCD calculations to non-zero values of
muB suggest that a critical point may exist in this region of the QCD phase
diagram. Discovery of the critical point or, equivalently, determining the
location where the phase transition from partonic to hadronic matter switches
from a smooth crossover to 1st order would establish a major landmark in the
phase diagram. Initial studies of Pb+Pb collisions in this energy range have
revealed several unexpected features in the data. In response to these results,
it has been suggested that the existing RHIC accelerator and experiments can be
used to further the investigation of this important physics topic. This
proceeding briefly summarizes the theoretical and experimental situation with
particular emphasis on the conclusions from a RIKEN BNL workshop held in March
of 2006.Comment: 8 pages, 2 figures, Conference Proceeding from Strangeness in Quark
Matter 2006, accepted for publication in J. Phys. G; Added final journal
reference and fixed typo in Ref
Single-Species Reactions on a Random Catalytic Chain
We present an exact solution for a catalytically-activated annihilation A + A
\to 0 reaction taking place on a one-dimensional chain in which some segments
(placed at random, with mean concentration p) possess special, catalytic
properties. Annihilation reaction takes place, as soon as any two A particles
land from the reservoir onto two vacant sites at the extremities of the
catalytic segment, or when any A particle lands onto a vacant site on a
catalytic segment while the site at the other extremity of this segment is
already occupied by another A particle. We find that the disorder-average
pressure per site of such a chain is given by , where is the
Langmuir adsorption pressure, (z being the activity and \beta^{-1} - the
temperature), while is the reaction-induced contribution, which
can be expressed, under appropriate change of notations, as the Lyapunov
exponent for the product of 2 \times 2 random matrices, obtained exactly by
Derrida and Hilhorst (J. Phys. A {\bf 16}, 2641 (1983)). Explicit asymptotic
formulae for the particle mean density and the compressibility are also
presented.Comment: AMSTeX, 17 pages, 1 figure, submitted to J. Phys.
Limits of space-times in five dimensions and their relation to the Segre Types
A limiting diagram for the Segre classification in 5-dimensional space-times
is obtained, extending a recent work on limits of the energy-momentum tensor in
general relativity. Some of Geroch's results on limits of space-times in
general relativity are also extended to the context of five-dimensional
Kaluza-Klein space-times.Comment: Late
U(1)SU(2) Gauge Invariance Made Simple for Density Functional Approximations
A semi-relativistic density-functional theory that includes spin-orbit
couplings and Zeeman fields on equal footing with the electromagnetic
potentials, is an appealing framework to develop a unified first-principles
computational approach for non-collinear magnetism, spintronics, orbitronics,
and topological states. The basic variables of this theory include the
paramagnetic current and the spin-current density, besides the particle and the
spin density, and the corresponding exchange-correlation (xc) energy functional
is invariant under local U(1)SU(2) gauge transformations. The xc-energy
functional must be approximated to enable practical applications, but, contrary
to the case of the standard density functional theory, finding simple
approximations suited to deal with realistic atomistic inhomogeneities has been
a long-standing challenge. Here, we propose a way out of this impasse by
showing that approximate gauge-invariant functionals can be easily generated
from existing approximate functionals of ordinary density-functional theory by
applying a simple {\it minimal substitution} on the kinetic energy density,
which controls the short-range behavior of the exchange hole. Our proposal
opens the way to the construction of approximate, yet non-empirical
functionals, which do not assume weak inhomogeneity and should therefore have a
wide range of applicability in atomic, molecular and condensed matter physics
Concentration of empirical distribution functions with applications to non-i.i.d. models
The concentration of empirical measures is studied for dependent data, whose
joint distribution satisfies Poincar\'{e}-type or logarithmic Sobolev
inequalities. The general concentration results are then applied to spectral
empirical distribution functions associated with high-dimensional random
matrices.Comment: Published in at http://dx.doi.org/10.3150/10-BEJ254 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
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