40 research outputs found
Sigma meson and lowest possible glueball candidate in an extended linear model
We formulate an extended linear model of a quarkonia nonet and a
tetraquark nonet as well as a complex iso-singlet (glueball) field to study the
low-lying scalar meson. Chiral symmetry and symmetry and their
breaking play important role to shape the scalar meson spectrum in our work.
Based on our study we will comment on what may be the mass of the lowest
possible scalar and pseudoscalar glueball states. We will also discuss on what
may be the nature of the sigma or meson.Comment: Contribution to the Proceedings of QCD@work 2012, Lecce, Italy, 18-21
June 2012, 5 pages, 2 figure
Interplay between chiral and deconfinement phase transitions
By using the dressed Polyakov loop or dual chiral condensate as an equivalent
order parameter of the deconfinement phase transition, we investigate the
relation between the chiral and deconfinement phase transitions at finite
temperature and density in the framework of three-flavor Nambu--Jona-Lasinio
(NJL) model. It is found that in the chiral limit, the critical temperature for
chiral phase transition coincides with that of the dressed Polyakov loop in the
whole plane. In the case of explicit chiral symmetry breaking, it is
found that the phase transitions are flavor dependent. For each flavor, the
transition temperature for chiral restoration is smaller than that
of the dressed Polyakov loop in the low baryon density region
where the transition is a crossover, and, the two critical temperatures
coincide in the high baryon density region where the phase transition is of
first order. Therefore, there are two critical end points, i.e,
and at finite density. We also explain the feature of
in the case of 1st and 2nd order phase transitions,
and in the case of crossover, and expect this feature
is general and can be extended to full QCD theory.Comment: 8 pages, 12 figures, proceedings for the International Workshop on
Hot and Cold Baryonic Matter 2010, Budapest, Aug. 15-20, 201
Chiral condensate and dressed Polyakov loop in the Nambu--Jona-Lasinio model
We investigate the chiral condensate and the dressed Polyakov loop or dual
chiral condensate at finite temperature and density in two-flavor
Nambu--Jona-Lasinio model. The dressed Polyakov loop is regarded as an
equivalent order parameter of deconfinement phase transition in a confining
theory. We find the behavior of dressed Polyakov loop in absence of any
confinement mechanism is quite interesting, with only quark degrees of freedom
present, it still shows an order parameter like behavior. It is found that in
the chiral limit, the critical temperature for chiral phase transition
coincides with that of the dressed Polyakov loop in the whole plane.
In the case of explicit chiral symmetry breaking, it is found that the
transition temperature for chiral restoration is smaller than that
of the dressed Polyakov loop in the low baryon density region
where the transition is a crossover. With the increase of current quark mass
the difference between the two transition temperatures is found to be
increasing. However, the two critical temperatures coincide in the high baryon
density region where the phase transition is of first order. We give an
explanation on the feature of in the case of 1st and
2nd order phase transitions, and in the case of
crossover, and expect this feature is general and can be extended to full QCD
theory. Our result might indicate that in the case of crossover, there exists a
small region where chiral symmetry is restored but the color degrees of freedom
are still confined.Comment: 7 pages, 10 figure
Susceptibilities and speed of sound from PNJL model
We present the Taylor expansion coefficients of the pressure in quark number
chemical potential , for the strongly interacting
matter as described by the PNJL model for two light degenerate flavours of
quarks u and d. The expansion has been done upto eighth order in , and
the results are consistent with recent estimates from Lattice. We have further
obtained the specific heat , squared speed of sound and the
conformal measure \cC.Comment: 13 pages, 8 figures, References added, some discussions on Fig. 4
modified, one table added, results unchanged, version to appear in Phys. Rev.
PNJL model with a Van der Monde term
We extend the Polyakov-Nambu-Jona-Lasinio (PNJL) model for two degenerate
flavours by including the effect of the SU(3) measure with a Van der Monde
(VdM) term. This ensures that the Polyakov loop always remains in the domain
[0,1]. The pressure, energy density, specific heat, speed of sound and
conformal measure show small or negligible effects from this term. However
various quark number and isospin susceptibilities are all found to approach
their respective ideal gas limits around 2 . We compare our methods with
other similar approaches in PNJL model and also present a quantitative
comparison with Lattice QCD data.Comment: 12 pages, 8 eps figures; extended discussion and reference added;
accepted in Phys. Rev.