A minimal quasiparticle approach for the QGP and its large-N c limits

Abstract

We propose a quasiparticle approach allowing to compute the equation of state of a generic gauge theory with gauge group SU(Nc) and quarks in an arbitrary representation. Our formalism relies on the thermal quasiparticle masses (quarks and gluons) computed from perturbative techniques, in which the standard two-loop running coupling constant is used. Our model is minimal in the sense that we do not allow any extra ansatz concerning the temperature-dependence of the running coupling. We first show that it is able to reproduce the most recent equations of state computed on the lattice for temperatures typically higher than 2 Tc. Well above Tc indeed, an ideal gas framework with thermal masses is indeed expected to be relevant. Then we study the accuracy of various inequivalent large-Nc limits concerning the description of the QCD results, as well as the equivalence between the QCDAS limit and the N = 1 SUSY Yang-Mills theory.PACS. 12.38.Mh -11.15.Pg 1 Remark that a quasiparticle description of hypothetical quark stars has been proposed historically as an application of the quark hypothesis, see [6].

Comments on a Minimal Quasiparticle Approach for the QGP and Its Large-N c Limits

“…1, the agreement between the model proposed in [1] and lattice data obtained in [18] is shown in the physically meaningful temperature range. Indeed, a strong hypothesis is required to apply the ideal-gas framework: The interactions between quasiparticles are neglected.…”

“…In this paper, we will summarize the description of the QGP as a quasiparticle approach proposed in [1] and add some new results. From a phenomenological point of view, quasiparticle models are based on the assumption that the QGP is made of deconfined quarks and gluons.…”

“…From a phenomenological point of view, quasiparticle models are based on the assumption that the QGP is made of deconfined quarks and gluons. In the approach [1], an ideal-gas framework has been used in order to compute the equations of state (EoS). These EoS have been compared with lattice EoS for different sectors (pure glue and full plasma) because of the lack of corresponding experimental data.…”

“…Pioneering works [2][3][4][5] have shown that the condition for quasiparticle approaches to reproduce the various EoS computed in lattice QCD is that the quasiparticles gain thermal masses that had mostly to be fitted to the lattice data. In [1], the thermal masses directly derived from Hard-Thermal-Loop (HTL) techniques in which a two-loop running coupling constant is used have been taken without ad hoc modification-see also e.g. the works [6][7][8] for a similar approach.…”

The SUSY Yang–Mills plasma in a T-matrix approach

“…formalism and the EoS of the medium would thus be given by a free gas of particles with HTL thermal masses, assuming V = 0. Such a model can be found in [48], where useful references about HTL results are given. Note finally that reaching pressure compatible with p SB demands huge temperatures: around 10 7 T c as shown in [49].…”