Abstract
The extent to which the dual meson condensates obtained in the Polyakov-loop enhanced linear sigma model can indicate deconfining transition is investigated by imposing the twisted boundary conditions. The influence of the improved unquenching effect, the dependence on the glue potential parametrization, and the role of the fermion vacuum contribution are focused on at the mean field level. At zero density, the rapid rise of the dual sigma condensate with $T$ is confirmed, which is more sensitive to the chiral transition than the increase of the Polyakov loop. For finite isospin chemical potential ${\ensuremath{\mu}}_{I}>{m}_{\ensuremath{\pi}}/2$, the dual sigma condensate shows abnormal thermal behavior which decreases with $T$ below the melting temperature ${T}_{c}^{{I}_{3}}$ of pion superfluidity. In contrast, the dual pion condensate always increases with $T$, with the maximum slope located at ${T}_{c}^{{I}_{3}}$ rather than ${T}_{c}^{P}$, as determined by the Polyakov loop. The dual vector meson condensate for ${\ensuremath{\mu}}_{I}>{m}_{\ensuremath{\pi}}/2$ is also more sensitive to the chiral restoration when considering the fermion vacuum contribution. The study suggests that the dual condensates calculated in this model are not appropriate indicators of deconfinement due to some limitations and uncertainty.
Highlights
Understanding the confinement-deconfinement phase transition at finite temperature and density is a very important task in high-energy nuclear physics
We mainly study the thermal property of the dual sigma condensate
We focus on roles of the fermion vacuum loop contribution, the parametrization of the glue potential, and the improved unquenching effect
Summary
Understanding the confinement-deconfinement phase transition at finite temperature and density is a very important task in high-energy nuclear physics. One merit of the DPL is that it interpolates between the quark condensate and Polyakov loop, which may imply some intrinsic relation between chiral transition and deconfinement Another is that it can be calculated in some effective theories or models of QCD. By considering gluon degrees of freedom with center symmetry, it is confirmed that the rapid rise of the DPL is still determined by chiral restoration rather than the increase of the Polyakov loop [27], where PNJL [28,29] is used.2 The main purpose of this work is to try to extract the DPL and other dual quantities in the Polyakov-loop augmented linear sigma model (PLσM) of QCD ( known as PQM) by taking into account the quark-improved glue potential and comparing it with the previous NJL results [25,26,27].
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