Instanton correlations in the finite temperature QCD vacuum (original) (raw)

Proceedings of the Mini-Workshop Quark Dynamics Bled , Slovenia , July 12 – 19 , 2004

At finite temperature, chiral quark models do not incorporate large gauge invariance which implies genuinely non-perturbative finite temperature gluonic degrees of freedom. Motivated by this observation, we describe how the coupling of the Polyakov loop as an independent degree of freedom to quarks not only accounts for large gauge invariance, but also allows to establish in a dynamical way the interaction between composite hadronic states such as Goldstone bosons to finite temperature non-perturbative gluons in a medium which can undergo a confinement-deconfinement phase transition. 1 Large Gauge Transformations One feature of gauge theories like QCD at finite temperatures in the imaginary time formulation [1–3] is the non-perturbative manifestation of the non Abelian gauge symmetry. In the Polyakov gauge, where ∂4A4 = 0 and A4 is a diagonal and traceless Nc ×Nc matrix, and Nc is the number of colors, there is still some freedom in choosing the gluon field. Let us consider for inst...

High-Density QCD and Instantons

Annals of Physics, 2000

Instantons generate strong non-perturbative interactions between quarks. In the vacuum, these interactions lead to chiral symmetry breaking and generate constituent quark masses on the order of 300-400 MeV. The observation that the same forces also provide attraction in the scalar diquark channel leads to the prediction that cold quark matter is a color superconductor, with gaps as large as ∼ 100 MeV. We provide a systematic treatment of color superconductivity in the instanton model. We show that the structure of the superconductor depends on the number of flavors. In the case of two flavors, we verify the standard scenario and provide an improved calculation of the mass gap. For three flavors, we show that the ground state is color-flavor locked and calculate the chiral condensate in the high density phase. We show that as a function of the strange quark mass, there is a sharp transition between the two phases. Finally, we go beyond the mean-field approximation and investigate the role of instanton-antiinstanton molecules, which-besides superconducting gap formation-provide a competitive mechanism for chiral restoration at finite density.

The QCD Vacuum as an Instanton Liquid

Annual Review of Nuclear and Particle Science, 1997

We review recent progress in understanding the importance of instanton effects in QCD. Instantons provide a mechanism for quark and gluon condensation, explain the U(1) A anomaly and the appearance of a non-perturbative vacuum energy density. In the framework of the instanton liquid model, a large number of hadronic correlation functions were calculated. The results are in good agreement with both experimental data and lattice simulations. We also review recent results on the phase structure of QCD-like theories. Instantons provide a mechanism for chiral symmetry restoration at finite temperature (or for a large number of quark flavors) connected with the formation of instanton-anti-instanton molecules.

Physics of hot hadronic matter and quark-gluon plasma

Nuclear Physics A, 1991

This Introductory talk contains a brief review of the current status of theoretical and experimental activities related to physics of superdense matter. In particular, we discuss latest lattice results on the phase transition, recent progress in chiral symmetry physics based on the theory of interacting instantons, news in the theory of QGP and of hot hadronic matter, mean pt and collective flow, the shape of pt distribution, strangeness production, J/ip suppression and 6 enhancement, two puzzles connected with soft pion and soft photon enhancements, and some other "ultrasoft" phenomena.

QCD instantons at finite temperature (I). Gluonic interactions and the fermion determinant

Nuclear Physics B, 1991

This is the first in a series of papers devoted to instanton-induced effects at non-zero temperatures. The main points will be the restoration of the chiral symmetry and the modification of the various correlation functions with increasing temperature. In this paper we investigate the temperature dependence of the gluonic and the quark-induced pseudo-particle interaction. We find that the gluonic interaction becomes much more long ranged, whereas the quark-induced interaction becomes exponentially short ranged.

Instantons and color symmetry breaking in the vacuum

2000

The instanton interaction in QCD generates an effective potential for scalar quark-antiquark condensates in the color singlet and octet channels. For three light quark flavors the cubic term in this potential induces an octet condensate and "spontaneous breaking" of color in the vacuum. Realistic masses of the ρ-and η ′ -mesons are compatible with renormalization-group-improved instanton perturbation theory. * We take the opportunity to correct the instanton vertex of . It was based on the Fierz transform of an uncorrect vertex quoted in .