QCD at high density/temperature

Investigations of deconfined quark matter within NJL-type models are reviewed, focusing on the regime of low temperatures and ``moderate'' densities, which is not accessible by perturbative QCD. Central issue is the interplay between chiral symmetry restoration and the formation of color superconducting phases. In order to lay a solid ground for this analysis, we begin with a rather detailed discussion of two and three-flavor NJL models and their phase structure, neglecting the possibility of diquark pairing in a first step. An important aspect of this part is a comparison with the MIT bag model. The NJL model is also applied to investigate the possibility of absolutely stable strange quark matter. In the next step the formalism is extended to include diquark condensates. We discuss the role and mutual influence of several conventional and less conventional quark-antiquark and diquark condensates. As a particularly interesting example, we analyze a spin-1 diquark condensate as a possible pairing channel for those quarks which are left over from the standard spin-0 condensate. For three-flavor systems, we find that a self-consistent calculation of the strange quark mass, together with the diquark condensates, is crucial for a realistic description of the 2SC-CFL phase transition. We also study the effect of neutrality constraints which are of relevance for compact stars. Both, homogeneous and mixed, neutral phases are constructed. Although neutrality constraints generally tend to disfavor the 2SC phase we find that this phase is again stabilized by the large values of the dynamical strange quark mass which follow from the self-consistent treatment. Finally, we combine our solutions with existing hadronic equations of state to investigate the existence of quark matter cores in neutron stars.Comment: Habilitation thesis, 193 pages, 63 figures; v2: minor changes, version to appear in Physics Report

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“…Upper right: Rajagopal (1999) [17]. Lower left: Alford (2003) [23]. Lower right: Schäfer (2003) [14].…”

Section: Introductionmentioning

confidence: 99%

“…[17]. More recently, further phases, like three-flavor color superconductors with condensed kaons (CFL-K) [18,19,20] or crystalline color superconductors ("LOFF phase") [21,22] have been suggested, which might partially (lower right diagram [14]) or even completely (lower left diagram [23]) replace the 2SC phase. Fig.…”

Section: Introductionmentioning

confidence: 99%

NJL-model analysis of dense quark matter

2005

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“…Lattice QCD simulations indicate that, at μ B ∼ 0, the transition from the hadronic phase to the quark-gluon plasma phase (QGP) is actually an analytic cross over [4][5][6][7][8][9]. At finite baryon densities μ B /T 1, however, lattice QCD calculations are affected by the sign problem [10][11][12][13], and, even a e-mail: guruprasadkadam18@gmail.com (corresponding author) b e-mail: hm@prl.res.in c e-mail: marco.panero@unito.it though very recent works, based on the analytical continuation from imaginary to real μ B , are now probing values of the chemical potential up to real μ B ∼ 300 MeV [14], results at large values of μ B are still scarce. Hence, in this regime of the phase diagram one has to resort to effective models of QCD, such as the Nambu-Jona-Lasinio model [15,16], the quarkmeson-coupling model [17] etc.…”

Section: Introductionmentioning

confidence: 99%

Critical exponents and transport properties near the QCD critical endpoint from the statistical bootstrap model

2021

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We present an estimate of the behavior of the shear and bulk viscosity coefficients when the QCD critical point is approached from the hadronic side, describing hadronic matter within the statistical bootstrap model of strong interactions. The bootstrap model shows critical behavior near the quark-hadron transition temperature if the parameter characterizing the degeneracy of Hagedorn states is properly chosen. We calculate the critical exponents and amplitudes of relevant thermodynamic quantities near the QCD critical point and combine them with an Ansatz for the shear and bulk viscosity coefficients to derive the behavior of these coefficients near the critical point. The shear viscosity to entropy density ratio is found to decrease when the temperature is increased, and to approach the Kovtun–Son–Starinets bound $$1/(4\pi )$$ 1 / ( 4 π ) faster near the critical point, while the bulk viscosity coefficient is found to rise very rapidly.

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“…Whereas in the standard conjectured QCD phase diagram [25], the spontaneous breaking of chiral symmetry inside the nuclear matter in bulk tends to restore as temperature increases, where there is no external constraints imposed (like the pressure) and the finite size effect is absent. Here we have seen that the strange quark mass relating to the spontaneous breaking of chiral symmetry becomes larger as the temperature increases for the strangelets with zero pressure.…”

Section: Resultsmentioning

confidence: 91%

Dynamical chiral symmetry breaking in strangelets at finite temperature

Ma,

Gao

2008

Preprint

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QCD at high density/temperature

Cited by 20 publications

References 138 publications

NJL-model analysis of dense quark matter

NJL-model analysis of dense quark matter

Critical exponents and transport properties near the QCD critical endpoint from the statistical bootstrap model

Dynamical chiral symmetry breaking in strangelets at finite temperature

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