4,527 research outputs found
Acceptance dependence of fluctuation measures near the QCD critical point
We argue that a crucial determinant of the acceptance dependence of
fluctuation measures in heavy-ion collisions is the range of correlations in
the momentum space, e.g., in rapidity, . The value of
for critical thermal fluctuations is determined by
the thermal rapidity spread of the particles at freezeout, and has little to do
with position space correlations, even near the critical point where the
spatial correlation length becomes as large as fm (this is in
contrast to the magnitudes of the cumulants, which are sensitive to ).
When the acceptance window is large, , the
cumulants of a given particle multiplicity, , scale linearly with
, or mean multiplicity in acceptance, , and
cumulant ratios are acceptance independent. While in the opposite regime,
, the factorial cumulants, ,
scale as , or . We demonstrate this general
behavior quantitatively in a model for critical point fluctuations, which also
shows that the dependence on transverse momentum acceptance is very
significant. We conclude that extension of rapidity coverage proposed by STAR
should significantly increase the magnitude of the critical point fluctuation
signatures.Comment: 9 pages, 4 figures, references adde
Quantum inequalities for massless spin-3/2 field in Minkowski spacetime
Quantum inequalities have been established for various quantum fields in both
flat and curved spacetimes. In particular, for spin-3/2 fields, Yu and Wu have
explicitly derived quantum inequalities for massive case. Employing the similar
method developed by Fewster and colleagues, this paper provides an explicit
formula of quantum inequalities for massless spin-3/2 field in four-dimensional
Minkowski spacetime.Comment: revtex4, 6 pages, accepted to be published in PRD, minor corrections,
typos correcte
Interacting dark energy, holographic principle and coincidence problem
The interacting and holographic dark energy models involve two important
quantities. One is the characteristic size of the holographic bound and the
other is the coupling term of the interaction between dark energy and dark
matter. Rather than fixing either of them, we present a detailed study of
theoretical relationships among these quantities and cosmological parameters as
well as observational constraints in a very general formalism. In particular,
we argue that the ratio of dark matter to dark energy density depends on the
choice of these two quantities, thus providing a mechanism to change the
evolution history of the ratio from that in standard cosmology such that the
coincidence problem may be solved. We investigate this problem in detail and
construct explicit models to demonstrate that it may be alleviated provided
that the interacting term and the characteristic size of holographic bound are
appropriately specified. Furthermore, these models are well fitted with the
current observation at least in the low red-shift region.Comment: 20 pages, 3 figure
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