71 research outputs found
Pressure and non-linear susceptibilities in QCD at finite chemical potentials
When the free energy density of QCD is expanded in a series in the chemical
potential, mu, the Taylor coefficients are the non-linear quark number
susceptibilities. We show that these depend on the prescription for putting
chemical potential on the lattice, making all extrapolations in chemical
potential prescription dependent at finite lattice spacing. To put bounds on
the prescription dependence, we investigate the magnitude of the non-linear
susceptibilities over a range of temperature, T, in QCD with two degenerate
flavours of light dynamical quarks at lattice spacing 1/4T. The prescription
dependence is removed in quenched QCD through a continuum extrapolation, and
the dependence of the pressure, P, on mu is obtained.Comment: 15 pages, 2 figures. Data on chi_uuuu added, discussion enhance
Impact of Z_2 monopoles and vortices on the deconfinement transition
The impact of Z_2-monopoles and vortices on the bulk and the deconfinement
phase transitions of the SU(2) lattice gauge theory with a mixed Villain form
of action is investigated by varying their numbers with appropriate chemical
potentials. Suppressing the former shifts the line of deconfinement transitions
in the coupling plane but it continues to behave also like the bulk transition
line. We find separate deconfinement and bulk phase transitions on the same
lattice, suggesting the two to be indeed coincident at higher adjoint
couplings. Universality is restored when both monopoles and vortices are
suppressed.Comment: LATTICE99(Finite Temp I), 3 pages, 3 eps figures, LaTeX, espcrc2.st
C-Periodicity and the Physical Mass in the 3-State Potts Model
The standard infinite-volume definition of connected correlation function and
particle mass in the 3-state Potts model can be implemented in Monte Carlo
simulations by using C-periodic spatial boundary conditions. This avoids both
the breaking of translation invariance (cold wall b.c.) and the phase-dependent
and thus possibly biased evaluation of data (periodic boundary cconditions).
The numerical feasibility of the standard definitions is demonstrated by sample
computations on a 24*24*48 lattice.Comment: 13 pages + 5 figures Preprint Nos. IC/93/131 and TIFR/TH/93-2
Sizing up the Nuclear Glue in -production
Nuclear gluon densities are of great importance to the physics of
relativistic heavy ion collisions, in particular, in assessing the origin of
-suppression. We describe our attempts to distinguish various models of
the gluonic EMC-effect, using the existing -production data in
proton-nucleus collisions. We find that no model is capable of explaining {\em
all} the features of the high precision E772 data although the overall trend
suggests this to be more a matter of fine-tuning the models than the presence
of new physical effects.Comment: Latex, 5 pages, 5 figures, as one uuencoded tarcompressed ps file.
espcrc1.sty required. added at the end of the script. TIFR/TH/93-35,
BU-TH-93/
Quenched QCD at finite temperature with overlap Fermions
We study quenched QCD just above the phase transition temperature using
overlap Fermions. Exact zero modes of the overlap operator are localized.
Chiral symmetry is restored, as indicated by the behavior of the chiral
condensate after subtracting the effects of zero modes. The vector and
pseudo-scalar screening masses are close to ideal gas values.Comment: Lattice2001(hightemp
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
A Lower Bound on in the O(4) Model on Anisotropic Lattices
Results of an investigation of the spin model at finite temperature
using anisotropic lattices are presented. In both the large approximation
and numerical simulations using the Wolff cluster algorithm we find that the
ratio of the symmetry restoration temperature to the Higgs mass
is independent of the anisotropy . From the numerical
simulations we obtain a lower bound of at a value for the Higgs mass , which is lowered
further by about at . Requiring certain timelike
correlation functions to coincide with their spacelike counterparts, quantum
and scaling corrections to the anisotropy are determined and are found to be
small, i.e., the anisotropy is found to be close to the ratio of spacelike and
timelike lattice spacings.Comment: 16 pages with 4 ps figures included. LaTeX file. BI-TP 92/27,
FSU-SCRI-92-101, HLRZ-92-40, TIFR/TH/92-4
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-
Quark number susceptibilities of hot QCD up to g^6ln(g)
The pressure of hot QCD has recently been determined to the last
perturbatively computable order g^6 ln(g) by Kajantie et al. using
three-dimensional effective theories. A similar method is applied here to the
pressure in the presence of small but non-vanishing quark chemical potentials,
and the result is used to derive the quark number susceptibilities in the limit
mu = 0. The diagonal quark number susceptibility of QCD with n_f flavours of
massless quarks is evaluated to order g^6ln(g) and compared with recent lattice
simulations. It is observed that the results qualitatively resemble the lattice
ones, and that when combined with the fully perturbative but yet undetermined
g^6 term they may well explain the behaviour of the lattice data for a wide
range of temperatures.Comment: 11 pages, 3 figures Typos corrected, references added, figures
modifie
Mesonic correlation lengths in high-temperature QCD
We consider spatial correlation lengths \xi for various QCD light quark
bilinears at temperatures above a few hundred MeV. Some of the correlation
lengths (such as that related to baryon density) coincide with what has been
measured earlier on from glueball-like states; others do not couple to
glueballs, and have a well-known perturbative leading-order expression as well
as a computable next-to-leading-order correction. We determine the latter
following analogies with the NRQCD effective theory, used for the study of
heavy quarkonia at zero temperature: we find (for the quenched case) \xi^{-1} =
2 \pi T + 0.1408 g^2 T, and compare with lattice results. One manifestation of
U_A(1) symmetry non-restoration is also pointed out.Comment: 25 pages. v2: small clarifications; published versio
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