arXiv subjects

E. V. Gorbar

Publications and source records attributed to E. V. Gorbar.

133 records · Page 8Linked to original sources

arXiv1999

Dynamical Symmetry Breaking in Spaces with Constant Negative Curvature

By using the Nambu-Jona-Lasinio model, we study dynamical symmetry breaking in spaces with constant negative curvature. We show that the physical reason for zero value of critical coupling value $g_c = 0$ in these spaces is connected with the effective reduction of dimension of spacetime $1 + D \to 1 + 1$ in the infrared region, which takes place for any dimension $1 + D$. Since the Laplace-Beltrami operator has a gap in spaces with constant negative curvature, such an effective reduction for scalar fields is absent and there are not problems with radiative corrections due to scalar fields. Therefore, dynamical symmetry breaking with the effective reduction of the dimension of spacetime for fermions in the infrared region is consistent with the Mermin-Wagner-Coleman theorem, which forbids spontaneous symmetry breaking in (1 + 1)-dimensional spacetime.

hep-th↗

arXiv1999

On the Effective Potential for Local Composite Operators

We show that the effective potential for local composite operators is a useful object in studing dynamical symmetry breaking by calculating the effective potential for the local composite operators $\barψ ψ$ and $ϕ^2$ in the Gross-Neveu (GN) and O(N) models, respectively. Since the effective potential for local composite operators can be calculated by using the Cornwall-Jackiw-Tomboulis (CJT) effective potential in theory with additional bare mass terms, we show that divergences in the effective potential for local composite operators are the same as in the CJT effective potential. We compare the results obtained with the results give by the auxiliary field method.

hep-th↗

arXiv1997

Chiral Symmetry Breaking in the Nambu-Jona-Lasinio Model in External Constant Electromagnetic Field

Dynamical chiral symmetry breaking (D$χ$SB) is studied in the Nambu-Jona-Lasinio model for an arbitrary combination of external constant electric and magnetic fields. In 3+1 dimensions it is shown that the critical coupling constant increases with increasing of the value of the second invariant of electromagentic field $\vec{E}\cdot\vec{B}$, i.e. the second invariant inhibits $DχSB$. The case of 2+1 dimensions is simpler because there is only one Lorentz invariant of electromagnetic field and any combination of constant fields can be reduced to cases either purely magnetic or purely electric field.

hep-th↗

arXiv1997

Heat Kernel Expansion for Operators in Spaces with Metric Incompatible with Connection

A method for calculation of the DWSG coefficients for operators in spaces with metric incompatible with connection is suggested based on a generalization of the pseudodifferential operators technique. By using the proposed method, the lowest DWSG coefficients are calculated for minimal operators of the second and fourth order and for nonminimal operators of the type $H^{μν} = - g^{μν} g_{αβ}\nabla^α\nabla^β + a\nabla^μ\nabla^ν + X^{μν}$ in spaces with metric incompatible with connection.

hep-th↗

arXiv1996

Crossover from BCS to Composite Boson (Local Pair) Superconductivity in Quasi-2D systems

The crossover from cooperative Cooper pairing to independent bound state (composite bosons) formation and condensation in quasi-2D systems is studied. It is shown that at low carrier density the critical superconducting temperature is equal to the temperature of Bose-condensation of ideal quasi-2D Bose-gas with heavy dynamical mass, meanwhile at high densities the BCS result remains valid. The evident nonmonotoneous behaviour of the critical temperature as function of the coupling constant (the energy of the two particle bound state) is a qualitative difference of quasi-2D crossover from 3D one.

cond-mat↗

arXiv1996

Heat Kernel Expansion for Operators of the Type of the Square Root of the Laplace Operator

A method is suggested for the calculation of the DeWitt-Seeley-Gilkey (DWSG) coefficients for the operator $\sqrt{-\nabla^2 + V(x)}$ basing on a generalization of the pseudodifferential operator technique. The lowest DWSG coefficients for the operator $\sqrt{-\nabla^2} + V(x)$ are calculated by using the method proposed. It is shown that the method admits a generalization to the case of operators of the type $(-\nabla^2 + V(X))^{1/{\rm m}}$, where m is an arbitrary rational number. A more simple method is proposed for the calculation of the DWSG coefficients for the case of strictly positive operators under the sign of root. By using this method, it is shown that the problem of the calculation of the DWSG coefficients for such operators is exactly solvable. Namely, an explicit formula expressing the DWSG coefficients for operators with root through the DWSG coefficients for operators without root is deduced.

hep-th↗

arXiv1993

Distance dependent statistics in a P,T-invariant model

It is shown that in the P,T-invariant model with the mixed Chern-Simons term the interaction of charge carriers leads to effective changing of their statistics, which depends on distance between them. In particular, in the limit of large distances fermions effectively turn into bosons.

hep-th↗