S. V. Molodtsov

Hot and dense gas of quark quasi-particles

Some features of hot and dense gas of quarks which are considered as the quasi-particles of the model Hamiltonian with four-fermion interaction are studied. Being adapted to the Nambu–Jona-Lasinio model this approach allows us to accommodate a phase transition similar to the nuclear liquid-gas one at the proper scale. It allows us to argue the existence of the mixed phase of vacuum and baryonic matter (even at zero temperature) as a plausible scenario of chiral symmetry (partial) restoration.

Some peculiarities in response to filling up the Fermi sphere with quarks

Considering quarks as the quasi-particles of the model Hamiltonian with four-fermion interaction we study response to the process of filling up the Fermi sphere with quarks, calculate the vacuum pressure and demonstrate the existence of filled-in state degenerate with the vacuum one.

Behavior of the gluon condensate in response to filling the Fermi sphere

The effect of the filling of the Fermi sphere with quarks of dynamically generated mass on the instanton liquid in a hot and dense strongly interacting medium is investigated. Among other things, it is shown that, in relation to the value characteristic of the Nambu-Jona-Lasinio model, the boundary of the phase transition restoring chiral invariance is shifted toward a greater chemical potential by about 100 MeV.

Quark induced excitations of the instanton liquid

Abstract The selfconsistent approach to the quark interactions in the instanton liquid is developed within the tadpole approximation calculating the basic functional integral. The effective Lagrangian obtained includes colorless scalar field interacting with quarks. The origin of this dynamical field as an interaction carrier in soft momentum region is discussed.

Correlation effects and bound states

Bound states in a simple quark model that are due to correlation effects are analyzed. The confining properties of this model in meson (quark-antiquark and diquark) channels manifest themselves at any quark momenta, and an extra potential field may only enhance the confining effect.

Some special features in the filling of the Fermi sphere with quark quasiparticles

The filling of the Fermi sphere with quarks treated as quasiparticles of the model Hamiltonian for four-fermion interaction is studied.

Phononlike Excitations of Instanton Liquid and New Scale of Non-Perturbative QCD

The phonon-like excitations of (anti)-instanton (ĪI) liquid due to adiabatic variations of vacuum wave functions are studied in this paper. The kinetic energy term is found and the proper effective Lagrangian for such excitations is evaluated. The properties of their spectrum, while corresponding masses are defined by ΛQCD,are investigated.

Fluctuation instability of the Dirac Sea in quark models of strong interactions

A number of exactly integrable (quark) models of quantum field theory that feature an infinite correlation length are considered. An instability of the standard vacuum quark ensemble, a Dirac sea (in spacetimes of dimension higher than three), is highlighted. It is due to a strong ground-state degeneracy, which, in turn, stems from a special character of the energy distribution. In the case where the momentumcutoff parameter tends to infinity, this distribution becomes infinitely narrow and leads to large (unlimited) fluctuations. A comparison of the results for various vacuum ensembles, including a Dirac sea, a neutral ensemble, a color superconductor, and a Bardeen–Cooper–Schrieffer (BCS) state, was performed. In the presence of color quark interaction, a BCS state is unambiguously chosen as the ground state of the quark ensemble.

Classical Gluon Fields and Collective Dynamics of Color-Charge Systems

An investigation of color fields that arise in collisions of relativistic heavy ions reveals that, in the non-Abelian case, a change in the color charge leads to the appearance of an extra term that generates a sizable contribution of color-charge glow in chromoelectric and chromomagnetic fields. The possibility of the appearance of a color echo in the scattering of composite color particles belonging to the dipole type is discussed. Arguments are adduced in support of the statement that such effects are of importance in simulating the first stage of ultrarelativistic heavy-ion collisions,where the initial parton state is determined by a high nonequilibrium parton density and by strong local color fluctuations.

Unexpected manifestation of quark condensation

A comparative analysis of some quark ensembles governed by a four-fermion interaction is performed. Arguments in support of the statement that the presence of a gas-liquid phase transition is a feature peculiar to them are adduced. The instability of small quark droplets is discussed and is attributed to the formation of a chiral soliton. The stability of baryon matter is due to a mixed phase of the vacuum and baryon matter.