arXiv subjects

N. O. Agasian

Publications and source records attributed to N. O. Agasian.

25 records · Page 2Linked to original sources

arXiv2000

Phase structure of the QCD vacuum in a magnetic field at low temperature

We study the QCD phase structure in magnetic field $H$ at low temperature $T$. The hadronic phase free energy in a constant homogeneous magnetic field is calculated in one-loop approximation of the chiral perturbation theory. The dependence of the quark and gluon condensates upon the temperature and field strength is found. It is shown that the chiral phase transition order parameter $<\bar q q>$ remains constant provided field strength and temperature are related via $H=const \cdot T^2$.

hep-ph↗

arXiv1999

The Quark and Gluon Condensates and Low-Energy QCD Theorems in a Magnetic Field

The low-energy QCD theorems are generalized in the presence of a constant magnetic field H. Two-loop approximation for the vacuum energy density in the framework of the chiral perturbation theory was obtained and the quark and gluon condensates were found as the functions of H.

hep-ph↗

arXiv1999

Instanton Screening in the Nonperturbative Gluodynamics

The gluon fields screening in the stochastic vacuum of gluodynamics is studied. The effective action is derived for the instanton interacting with nonperturbative fields. Quantum nonperturbative effects are shown to affect greatly the shape of instanton. The power asymptotics x^2 of the classical "instanton's profile function" at large distances is replaced due to these effects by Airy function asymptotics.

hep-ph↗

arXiv1999

Nonperturbative QCD vacuum and Colour Superconductivity

We discuss the possibility of existence of colour superconducting state in real QCD vacuum with nonzero gluon condensate. We argue, that nonperturbative gluonic fields might play a crucial role in colour superconductivity scenario.

hep-ph↗

arXiv1998

Effects of Screening of the Instantons in Nonperturbative QCD

The gluon fields screening in the stochastic vacuum of gluodynamics is studied. The effective action is derived for the instanton interacting with nonperturbative fields. Quantum nonperturbative effects are shown to affect greatly the shape of instanton. The power asymptotics x^{-2} of the classical "instanton's profile function" at large distances is replaced due to yhese effects by Airy function asymptotics x^{-1/4} exp(-const\cdot x^{3/2}).

hep-ph↗

arXiv1997

Modelling the QCD Phase Transition with an Effective Lagrangian of Light and Massive Hadrons

The temperature dependence of quark and gluon condensates in QCD as precursor of the chiral and deconfining phase transition is modelled with a conformally extended non-linear sigma-model including broken chiral and scale invariance. The model is further enlarged by including (free) heavier hadrons. Within this frame we then study the interplay of QCD scale breaking effects and heavier hadrons in chiral symmetry restoration.

hep-ph↗

arXiv1997

Phase Structure and Nonperturbative States in Three-Dimensional Adjoint Higgs Model

The thermodynamics of 3d adjoint Higgs model is considered. We study the properties of the Polyakov loop correlators and the critical behavior at the deconfinement phase transition. Our main tool is a reduction to the 2d sine-Gordon model. The Polyakov loops appear to be connected with the soliton operators in it. The known exact results in the sine-Gordon theory allow us to study in detail the temperature dependence of the string tension, as well as to get some information about a nonperturbative dynamics in the confinement phase. We also consider the symmetry restoration at high temperature which makes it possible to construct the phase diagram of the model completely.

hep-th↗