1,339,188 research outputs found
QCD Critical Point in a Quasiparticle Model
Recent theoretical investigations have unveiled a rich structure in the
quantum chromodynamics (QCD) phase diagram which consists of quark gluon plasma
(QGP) and the hadronic phases but also supports the existence of a cross-over
transition ending at a critical end point (CEP). We find a too large variation
in determination of the coordinates of the CEP in the temperature (T), baryon
chemical potential () plane and, therefore, its identification in the
current heavy-ion experiments becomes debatable. Here we use an equation of
state (EOS) for a deconfined QGP using a thermodynamically consistent
quasiparticle model involving quarks and gluons having thermal masses. We
further use a thermodynamically consistent excluded volume model for the hadron
gas (HG) which was recently proposed by us. Using these equations of state, a
first order deconfining phase transition is constructed using Gibbs' criteria.
This leads to an interesting finding that the phase transition line ends at a
critical point (CEP) beyond which a cross-over region exists. Using our thermal
HG model, we obtain a chemical freeze out curve and we find that the CEP lies
in close proximity to this curve as proposed by some authors. The coordinates
of CEP are found to lie within the reach of RHIC experiment.Comment: 15 pages, 3 figures, 1 table; minor corrections, to be appeared in
Phys. Rev.
Nonuniversal Effects in the Homogeneous Bose Gas
Effective field theory predicts that the leading nonuniversal effects in the
homogeneous Bose gas arise from the effective range for S-wave scattering and
from an effective three-body contact interaction. We calculate the leading
nonuniversal contributions to the energy density and condensate fraction and
compare the predictions with results from diffusion Monte Carlo calculations by
Giorgini, Boronat, and Casulleras. We give a crude determination of the
strength of the three-body contact interaction for various model potentials.
Accurate determinations could be obtained from diffusion Monte Carlo
calculations of the energy density with higher statistics.Comment: 24 pages, RevTex, 5 ps figures, included with epsf.te
Density Fluctuations in the Oscillatory Phase of Nonclassical Inflaton in FRW Universe
Using coherent and squeezed state formalisms of quantum optics for a
minimally coupled non-classical inflaton in the FRW mertic is studied, in
semiclassical theory of gravity. The leading order solution for the
semiclassical Einstein equations in the coherent, squeezed and squeezed vacuum
states are obtained perturbatively and are exhibit powerlaw expansion
behaviour. The validity of the semiclassical theory is examined in the squeezed
vacuum state in the oscillatory phase of the inflaton. The semiclassical theory
in the oscillatory phase of the non-classical inflaton holds only if the
associated squeezing parameter is much less compared to unity. Quantum
fluctuations of the inflaton is also examined in coherent and squeezed state
formalisms.Comment: 14 pages, 2 figures, To appear in Int.J.Mod.Phys.
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