Self-Consistent Approximations in Relativistic Plasmas: Quasiparticle Analysis of the Thermodynamic Properties

Vanderheyden, Benoît; Baym, Gordon

doi:10.1023/b:joss.0000033166.37520.ae

Cited by 93 publications

(106 citation statements)

References 25 publications

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“…Thus, any explicit two-loop interaction contribution to the entropy has been absorbed into the spectral properties of quasiparticles. Remarkably, this holds equally true for fermionic [240] and gluonic [31,32] interactions. The expression (5.45) is manifestly UV finite, the statistical factors providing an ultraviolet cut-off.…”

Section: Other Resummations and Lattice Calculationsmentioning

confidence: 79%

The quark–gluon plasma: collective dynamics and hard thermal loops

Blaizot¹,

Iancu²

2002

Physics Reports

515

714

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We present a unified description of the high temperature phase of QCD, the so-called quark-gluon plasma, in a regime where the effective gauge coupling g is sufficiently small to allow for weak coupling calculations. The main focuss is the construction of the effective theory for the collective excitations which develop at a typical scale gT , which is well separated from the typical energy of single particle excitations which is the temperature T . We show that the short wavelength thermal fluctuations, i.e., the plasma particles, provide a source for long wavelength oscillations of average fields which carry the quantum numbers of the plasma constituents, the quarks and the gluons. To leading order in g, the plasma particles obey simple gauge-covariant kinetic equations, whose derivation from the general Dyson-Schwinger equations is outlined. By solving these equations, we effectively integrate out the hard degrees of freedom, and are left with an effective theory for the soft collective excitations. As a by-product, the "hard thermal loops" emerge naturally in a physically transparent framework. We show that the collective excitations can be described in terms of classical fields, and develop for these a Hamiltonian formalism. This can be used to estimate the effect of the soft thermal fluctuations on the correlation functions. The effect of collisions among the hard particles is also studied. In particular we discuss how the collisions affect the lifetimes of quasiparticle excitations in a regime where the mean free path is comparable with the range of the relevant interactions. Collisions play also a decisive role in the construction a Member of CNRS. E-mail: blaizot@spht.saclay.cea.fr b Member of CNRS. E-mail: iancu@spht.saclay.cea.fr c Laboratoire de la Direction des Sciences de la Matière du Commissariatà l'Energie Atomique of the effective theory for ultrasoft excitations, with momenta ∼ g 2 T , a topic which is briefly addressed at the end of this paper.

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Section: Other Resummations and Lattice Calculationsmentioning

confidence: 79%

The quark–gluon plasma: collective dynamics and hard thermal loops

Blaizot¹,

Iancu²

2002

Physics Reports

515

714

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“…As discussed in Refs. [21,22], one simple solution to this problem is to start with the entropy density S rather than P or ǫ. Up to higher-order corrections which we shall review in a moment, the entropy density of a quasi-particle gas is given by the naive ideal gas formula,…”

Section: Discussionmentioning

confidence: 99%

Bulk viscosity of high-temperature QCD

2006

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We compute the bulk viscosity ζ of high-temperature QCD to leading order in powers of the running coupling α s (T ). We find that it is negligible compared to shear viscosity η for any α s that might reasonably be considered small. The physics of bulk viscosity in QCD is a bit different than in scalar φ 4 theory. In particular, unlike in scalar theory, we find that an old, crude estimate of ζ ≃ 15 1 3 − v 2 s 2 η gives the correct order of magnitude, where v s is the speed of sound. We also find that leading-log expansions of our result for ζ are not accurate except at very small coupling.

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“…For two light flavors (N f = 2) some comparison can be made in the low temperature (and low µ) range. Unfortunately the simple scaling relation (39) does not hold at small T such that an explicit comparison has to be presented between the DQPM for N f = 2 and the lQCD calculations from Ref. [60].…”

Section: Finite Quark Chemical Potential µ Qmentioning

confidence: 99%

Dynamical quasiparticles properties and effective interactions in the sQGP

2007

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Dynamical quasiparticle properties are determined from lattice QCD along the line of the Peshier model for the running strong coupling constant in case of three light flavors. By separating time-like and space-like quantities in the number density and energy density the effective degrees of freedom in the gluon and quark sector may be specified from the time-like densities. The space-like parts of the energy densities are identified with interaction energy (or potential energy) densities. By using the timelike parton densities (or scalar densities) as independent degrees of freedom -instead of the temperature T and chemical potential µ q as Lagrange parameters -variations of the potential energy densities with respect to the time-like gluon and/or fermion densities lead to effective mean-fields for time-like gluons and quarks as well as to effective gluon-gluon, quark-gluon and quark-quark (quark-antiquark) interactions. The latter dynamical quantities are found to be approximately independent on the quark chemical potential µ q and thus well suited for an inplementation in offshell parton transport approaches. Results from the dynamical quasiparticle model (DQPM) in case of two dynamical light quark flavors are compared to lattice QCD calculations for the net quark density ρ q (T, µ q ) as well as for the 'back-to-back' differential dilepton production rate by q −q annihilation. The DQPM is found to pass the independent tests.

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Self-Consistent Approximations in Relativistic Plasmas: Quasiparticle Analysis of the Thermodynamic Properties

Cited by 93 publications

References 25 publications

The quark–gluon plasma: collective dynamics and hard thermal loops

The quark–gluon plasma: collective dynamics and hard thermal loops

Bulk viscosity of high-temperature QCD

Dynamical quasiparticles properties and effective interactions in the sQGP

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