QCD Deconfinement Research Articles

Chiralspin symmetry and confinement

Interesting lattice QCD simulations at high temperature in QCD and particular truncated studies have shown the emergence of an unexpected group symmetry, so called chiralspin. However this is not a symmetry of the QCD action for free quarks, which makes unclear the transition to deconfinement at high temperature in QCD. Therefore we try to redefine this group so that is a symmetry of free quark action and it is consistent with the presence of deconfinement in QCD.

Erratum: Chiral symmetry restoration and deconfinement in QCD at finite temperature [Phys. Rev. D86, 034030 (2012)

Erratum: Chiral symmetry restoration and deconfinement in QCD at finite temperature [Phys. Rev. D<b>86</b>, 034030 (2012)

Chiral symmetry restoration and deconfinement in QCD at finite temperature

The light-quark correlator in the axial-vector channel is used, in conjunction with finite energy QCD sum rules at finite temperature, in order to (a) establish a relation between chiral-symmetry restoration and deconfinement, and (b) determine the temperature behavior of the $a_1(1260)$ width and coupling. Results indicate that deconfinement takes place at a slightly lower temperature than chiral-symmetry restoration, although this difference is not significant given the accuracy of the method. The behaviour of the $a_1(1260)$ parameters is consistent with quark-gluon deconfinement, as the width grows and the coupling decreases with increasing temperature.

MONOPOLES FROM QUARK CONDENSATES IN QCD

Chiral monopoles are hedgehoglike structures in local chiral condensates in QCD. These monopoles are (i) made of quark and gluon fields; (ii) explicitly gauge-invariant; (iii) they carry quantized and conserved chromomagnetic charge. We argue that the chiral condensate vanishes in a core of the chiral monopole while the density of these monopoles increases with temperature wiping out the quark condensate in quark-gluon plasma. We suggest that the chiral monopoles are responsible for the chiral symmetry restoration in QCD. We also argue that the chiral monopoles are unlikely to be responsible for confinement of color. Thus, phenomena of the chiral symmetry restoration and the color deconfinement in QCD are not necessarily related to each other and the corresponding transitions may happen at different temperatures.

Chiral transition and deconfinement in QCD

The study of QCD with two light dynamical fermions is of fundamental importance to understand the mechanism of color confinement. We present results of a numerical investigation on the order of the chiral phase transition with N f = 2 by use of a novel strategy in finite size scaling analysis. We compare the critical behaviour of the specific heat, of the chiral susceptibility and of the equation of state with the possible critical behaviours. A second order transition in the O(4) and O(2) universality classes are excluded by our data and substantial evidence emerges for a first order transition. Like in most of previous works we have used the standard staggered action with L t = 4 : possible scaling violations and the need for further studies are discussed.

Connection between chiral symmetry restoration and deconfinement

We propose a simple explanation for the connection between chiral symmetry restoration and deconfinement in QCD at high temperature. In the Higgs description of the QCD vacuum both spontaneous chiral symmetry breaking and effective gluon masses are generated by the condensate of a color octet quark-antiquark pair. The transition to the high-temperature state proceeds by the melting of this condensate. Quarks and gluons become (approximately) massless at the same critical temperature. For instanton-dominated effective multiquark interactions and three light quarks with equal mass we find a first order phase transition at a critical temperature around 170 MeV.

Cluster percolation and thermal critical behavior

Continuous phase transitions in spin systems can be formulated as percolation of suitably defined clusters. We review this equivalence and then discuss how in a similar way, the color deconfinement transition in SU(2) gauge theory can be treated as a percolation phenomenon. In the presence of an external field, spin systems cease to show thermal critical behavior, but the geometric percolation transition persists (Kertész line). For H≠0, we study the relation between percolation and pseudocritical behavior, both for continuous and first order transitions, and show that it leads to the necessity of an H-dependent cluster definition. A viable formulation of this kind could serve as a definition of deconfinement in QCD with dynamical quarks.

Quark confinement and deconfinement in QCD from the viewpoint of Abelian-projected effective gauge theory

We give another derivation of quark confinement in QCD from the viewpoint of the low-energy effective Abelian gauge theory of QCD obtained via Abelian projection. It is based on the recently discovered Berezinskii-Kosterlitz-Thouless phase transition in the four-dimensional Abelian gauge theory. Moreover, we show that there exists a critical gauge coupling constant in QCD, above which confinement set in and below which there is no confinement. In a SU( N) gauge theory with N f flavored fermions, we argue that this leads to a critical value of fermion flavors N f c for the confinement as well as the chiral symmetry breaking, which separates the deconfining and chiral symmetric phase from the confining and chiral symmetry breaking phase. A finite-temperature deconfinement transition is also discussed briefly.

Deconfinement in QCD with Dynamical Quarks

We study the phase structure of full QCD within the canonical ensemble (CE) with respect to triality in a lattice formulation. The procedure to calculate the effective potentials (EP) in the CE is given. We calculate the EP for the three-dimensional SU(2) gauge model at finite temperature in the strong coupling region. The potential exhibits a genuine deconfinement phase transition unlike the similar potential obtained in the grand canonical ensemble (GCE). Furthermore, we investigate the EP with the chiral condensate included. Contrary to other recent results we find chiral symmetry restoration in all triality sectors. Dealing with massless staggered fermions we observe chiral symmetry restoration accompanying a deconfinement phase transition of first-order. Above the critical point, besides two Z(2) symmetric "deconfining" vacua there exists a metastable "confining" vacuum in a wide region of the (Nt,γ)-plane. Such a picture could be interpreted as an indication for a mixed state of hadrons and quarks in the vicinity of the critical line.

Transition to colour deconfinement in QCD

Transition to colour deconfinement in QCD

Colour deconfinement in QCD at finite temperature

Colour deconfinement in QCD at finite temperature

Deconfinement in QCD: An analysis of the phase transition

I discuss the Ape group results concerning the deconfining transition in finite temperature lattice quantum chromodynamics. I discuss in detail our evidence for a very large correlation length at the critical point, suggestive of a weak first order or second order transition. I discuss methods and observable quantities (source, smearing, blocking), the details of the numerical simulations (finite separation mass estimators, fits), measurements of the correlation length in the glue ball channels, the three-dimensional three-state Potts model.

STRANGE MATTER, DETONATIONS AND SUPERNOVAE

We present a possible scenario driven by QCD deconfinement in a high density nuclear matter medium. Some expected consequences for type II supernovae explosions are also given, particularly, the output energy that might be enough to account for the observed events.

Deconfinement and chiral-symmetry restoration in finite-temperature lattice QCD.

Using a mean-field method we obtain some qualitative results regarding the phase diagram of this theory. Emphasis is given to the interdependence between chiral-symmetry restoration and deconfinement. For the coupling constant below a given value, where what is left of deconfinement penetrates enough into the broken-chiral-symmetry phase, we find a line of first-order phase transitions even for vanishing bare-quark mass.