169 research outputs found
Phase Transitions in SO(3) Lattice Gauge Theory
The phase diagram of SO(3) lattice gauge theory is investigated by Monte
Carlo techniques on both symmetric and asymmetric lattices with a view (i) to
understanding the relationship between the bulk transition and the
deconfinement transition, and (ii) to resolving the current ambiguity about the
nature of the high temperature phase. A number of tests, including an
introduction of a magnetic field and measurement of different correlation
functions in the phases with positive and negative values for the adjoint
Polyakov line, lead to the conclusion that the two phases correspond to the
same physical state. Studies on lattices of different sizes reveal only one
phase transition for this theory on all of them and it appears to have a
deconfining nature.Comment: Latex 19 pages, 9 figures. Minor changes in introduction and summary
sections. The version that appeared in journa
Z2 Monopoles, Vortices, and the Deconfinement Transition in Mixed Action SU(2) Gauge Theory
Adding separate chemical potentials lambda and gamma for Z2 monopoles and
vortices respectively in the Villain form of the mixed fundamental-adjoint
action for the SU(2) lattice gauge theory, we investigate their role in the
interplay between the deconfinement and bulk phase transitions using Monte
Carlo techniques. Setting lambda to be nonzero, we find that the line of
deconfinement transitions is shifted in the coupling plane but it behaves
curiously also like the bulk transition line for large enough adjoint coupling,
as for lambda=0. In a narrow range of couplings, however, we find separate
deconfinement and bulk phase transitions on the same lattice for nonzero and
large lambda, suggesting the two to be indeed coincident in the region where a
first order deconfinement phase transition is seen. In the limit of large
lambda and gamma, we obtain only lines of second order deconfinement phase
transitions, as expected from universality.Comment: 18 pages, 10 figures include
Quark-Gluon Plasma: Status of Heavy Ion Physics
Lattice quantum chromodynamics (QCD), defined on a discrete space time
lattice, leads to a spectacular non-perturbative prediction of a new state of
matter, called quark-gluon plasma (QGP), at sufficiently high temperatures or
equivalently large energy densities. The experimental programs of CERN, Geneva
and BNL, New York of relativistic heavy ion collisions are expected to produce
such energy densities, thereby providing us a chance to test the above
prediction. After a brief introduction of the necessary theoretical concepts, I
will present a critical review of the experimental results already obtained by
the various experiments in order to examine whether QGP has already been
observed by them.Comment: 11 Pages, LaTeX, Plenary talk given at 6th Workshop in High Energy
Physics Phenomenology (WHEPP 6), Chennai (Madras), India, 3-15 Jan 2000 To
appear in Pramana, Journal of Physic
The continuum limit of quark number susceptibilities
We report the continuum limit of quark number susceptibilities in quenched
QCD. Deviations from ideal gas behaviour at temperature T increase as the
lattice spacing is decreased from T/4 to T/6, but a further decrease seems to
have very little effect. The measured susceptibilities are 20% lower than the
ideal gas values, and also 10% below the hard thermal loop (HTL) results. The
off-diagonal susceptibility is several orders of magnitude smaller than the HTL
results. We verify a strong correlation between the lowest screening mass and
the susceptibility. We also show that the quark number susceptibilities give a
reasonable account of the Wroblewski parameter, which measures the strangeness
yield in a heavy-ion collision.Comment: 8 pages, 5 figure
Potts Flux Tube Model at Nonzero Chemical Potential
We model the deconfinement phase transition in quantum chromodynamics at
nonzero baryon number density and large quark mass by extending the flux tube
model (three-state, three-dimensional Potts model) to nonzero chemical
potential. In a direct numerical simulation we confirm mean-field-theory
predictions that the deconfinement transition does not occur in a baryon-rich
environment.Comment: 14 pp RevTeX, 10 Postscript figures, submitted to Phys. Rev D.
(Corrected some typographical errors.
A transport coefficient: the electrical conductivity
I describe the lattice determination of the electrical conductivity of the
quark gluon plasma. Since this is the first extraction of a transport
coefficient with a degree of control over errors, I next use this to make
estimates of other transport related quantities using simple kinetic theory
formulae. The resulting estimates are applied to fluctuations, ultra-soft
photon spectra and the viscosity. Dimming of ultra-soft photons is exponential
in the mean free path, and hence is a very sensitive probe of transport.Comment: Talk given in ICPAQGP 2005, SINP, Kolkat
Quark Number Susceptibility and Thermodynamics in HTL approximation
In HTL perturbation theory we obtain leading order quark number
susceptibility as a response to an external disturbance, viz., chemical
potential (\mu) that generates density fluctuation, which is related to the
correlation function through the thermodynamic sum rule associated with the
symmetry of the system. We also obtain various thermodynamic quantities in
leading order.Comment: 4 pages, 2 figures, Talk given at the 6th ICPAQGP-2010, Goa, India,
December 6-10, 201
Quantum structure of the non-Abelian Weizsacker-Williams field for a very large nucleus
We consider the McLerran-Venugopalan model for calculation of the small-
part of the gluon distribution function for a very large ultrarelativistic
nucleus at weak coupling. We construct the Feynman diagrams which correspond to
the classical Weizs\"{a}cker-Williams field found previously [Yu. V. Kovchegov,
Phys. Rev. D 54, 5463 (1996)] as a solution of the classical equations of
motion for the gluon field in the light-cone gauge. Analyzing these diagrams we
obtain a limit for the McLerran-Venugopalan model. We show that as long as this
limit is not violated a classical field can be used for calculation of
scattering amplitudes.Comment: 13 pages, REVTeX, 9 figure
Introduction of the chemical potential in the overlap formalism
We investigate the possibility of coupling a chemical potential only to the
physical chiral fermions on the lattice starting from the many body state
description of overlap fermions. After developing the formalism for a chiral
gauge theory, we focus our attention on the case of free fermions coupled to a
vector like chemical potential and discuss the issue of zero temperature
divergences.Comment: 17 pages, 3 figures, minor changes to v1, version to appear in JHE
Heavy Flavor Hadrons in Statistical Hadronization of Strangeness-rich QGP
We study b, c quark hadronization from QGP. We obtain the yields of charm and
bottom flavored hadrons within the statistical hadronization model. The
important novel feature of this study is that we take into account the high
strangeness and entropy content of QGP, conserving strangeness and entropy
yields at hadronization.Comment: v2 expended: 20 pages, 23 figures, 5 tables, in press EPJ-
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