Lattice QCD: bulk and transport properties of QCD matter

Ratti, Claudia

doi:10.1016/j.nuclphysa.2016.02.022

Cited by 10 publications

(16 citation statements)

References 65 publications

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“…At zero chemical potential, numerical simulations on the lattice indicate that there is no true phase transition, just a crossover, albeit one where the degrees of freedom increase dramatically [2][3][4]. At a nonzero chemical potential, however, a crossover line may meet a line of first order transitions at a critical endpoint [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Fluctuations in cool quark matter and the phase diagram of quantum chromodynamics

2019

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We consider the phase diagram of hadronic matter as a function of temperature, T , and baryon chemical potential, µ. Currently the dominant paradigm is a line of first order transitions which ends at a critical endpoint.In this work we suggest that spatially inhomogenous phases are a generic feature of the hadronic phase diagram at nonzero µ and low T . Familiar examples are pion and kaon condensates. At higher densities, we argue that these condensates connect onto chiral spirals in a quarkyonic regime.Both of these phases exhibit the spontaneous breaking of a global U (1) symmetry and quasi-long range order, analogous to smectic liquid crystals. We argue that there is a continuous line of first order transitions which separate spatially inhomogenous from homogenous phases, where the latter can be either a hadronic phase or a quark-gluon plasma.While mean field theory predicts that there is a Lifshitz point along this line of first order transitions, in three spatial dimensions strong infrared fluctuations wash out any Lifshitz point.Using known results from inhomogenous polymers, we suggest that instead there is a Lifshitz regime. Non-perturbative effects are large in this regime, where the momentum dependent terms for the propagators of pions and associated modes are dominated not by terms quadratic in momenta, but quartic. Fluctuations in a Lifshitz regime may be directly relevant to the collisions of heavy ions at (relatively) low energies, √ s/A : 1 → 20 GeV. A quarkyonic phase only exists when quark excitations near the Fermi surface are (effectively) confined. While for three colors numerical simulations of lattice gauge theories at nonzero quark density are afflicted by the sign problem for three colors, they are possible for two colors [118-123]. Although the original argument for a quarkyonic phase was based upon the limit of a large number of colors [102], these simulations show that even for two colors, the expectation value of the Polyakov loop is small, indicating confinment, up to large values of the quark chemical potential [118-123]. Directly relevant to our analysis are the results of Bornyakov et al., who find that the string tension decreases gradually from its value in vacuum, to essentially zero at µ q ∼ 750 MeV: see Fig. 3 of Ref. [123]. This suggests

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Section: Introductionmentioning

confidence: 99%

Fluctuations in cool quark matter and the phase diagram of quantum chromodynamics

2019

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“…Note that, contrary to the q-NJL model [16], the qz-QPM model is formulated in such a way as to reproduce the effective fugacities of the original z-QPM [32], which, in turn, describes the lattice QCD results [46,47]. This means that the qz-QPM also describes them; in fact they serve as a kind of experimental data.…”

Section: Discussionmentioning

confidence: 99%

Nonextensive Quasiparticle Description of QCD Matter

Rożynek¹,

Wilk²

2019

Symmetry

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The dynamics of QCD matter is often described using effective mean field (MF) models based on Boltzmann-Gibbs (BG) extensive statistics. However, such matter is normally produced in small packets and in violent collisions where the usual conditions justifying the use of BG statistics are not fulfilled and the systems produced are not extensive. This can be accounted for either by enriching the original dynamics or by replacing the BG statistics by its nonextensive counterpart described by a nonextensivity parameter q = 1 (for q → 1 one returns to the extensive situation). In this work we investigate the interplay between the effects of dynamics and nonextensivity. Since the complexity of the nonextensive MF models prevents their simple visualization, we instead use some simple quasi-particle description of QCD matter in which the interaction is modelled phenomenologically by some effective fugacities, z. Embedding such a model in a nonextensive environment allows for a well-defined separation of the dynamics (represented by z) and the nonextensivity (represented by q) and a better understanding of their relationship.

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“…More recently, preliminary results have been shown for a combined fit of χ 1 /χ 2 for electric charge and baryon number, which allows to extract both freeze-out T and µ B at a given collision energy [45]. The results are shown in the left panel of figure 3.…”

Section: Fluctuations Of Conserved Chargesmentioning

confidence: 97%

“…Figure 3. Left: Preliminary results of the WB collaboration [45]. The colored full and dashed lines are the contours at constant mean/variance ratios of the net electric charge from lattice simulations.…”

Section: Fluctuations Of Conserved Chargesmentioning

confidence: 99%