180 research outputs found
Calculation of the Pseudoscalar-Isoscalar Hadronic Current Correlation Functions of the Quark-Gluon Plasma
We report the results of calculations of pseudoscalar-isoscalar hadronic
current correlators using the Nambu--Jona-Lasinio model and the real-time
finite-temperature formalism. Results are presented for the temperatures range
1.2 6.0, where is the temperature of the
confinement-deconfinement transition, which we take to be MeV. Two
important resonant features are seen in our calculations. In order to
understand the origin of these resonances, we have performed relativistic
random phase approximation (RPA)calculations of the temperature-dependent
spectrum of the mesons for . For the RPA calculations, use is
made of a simple model in which we introduce temperature- dependent constituent
quark masses calculated in a mean-field approximation and a
temperature-dependent confining interaction whose form is motivated by recent
studies made using lattice simulations of QCD with dynamical quarks. We also
introduce temperature-dependent coupling constants in our generalized NJL
model. Our motivation in the latter case is the simulation of the approach to a
weakly interacting system at high temperatures. We present some evidence that
supports our use of temperature-dependent coupling constants for the NJL model.
We suggest that our results may be of interest to researchers who use lattice
simulations of QCD to obtain temperature dependent spectral functions for
various hadronic current correlation functions.Comment: 20 pages, 10 figures, Revtex
Description of Gluon Propagation in the Presence of an A^2 Condensate
There is a good deal of current interest in the condensate A^2 which has been
seen to play an important role in calculations which make use of the operator
product expansion. That development has led to the publication of a large
number of papers which discuss how that condensate could play a role in a
gauge-invariant formulation. In the present work we consider gluon propagation
in the presence of such a condensate which we assume to be present in the
vacuum. We show that the gluon propagator has no on-mass-shell pole and,
therefore, a gluon cannot propagate over extended distances. That is, the gluon
is a nonpropagating mode in the gluon condensate. In the present work we
discuss the properties of both the Euclidean-space and Minkowski-space gluon
propagator. In the case of the Euclidean-space propagator we can make contact
with the results of QCD lattice calculations of the propagator in the Landau
gauge. With an appropriate choice of normalization constants, we present a
unified representation of the gluon propagator that describes both the
Minkowski-space and Euclidean-space dynamics in which the A^2 condensate plays
an important role.Comment: 28 pages, 11 figure
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