arXiv subjects

S. V. Esaibegyan

Publications and source records attributed to S. V. Esaibegyan.

4 recordsLinked to original sources

arXiv1999

Gluon Field Strength Correlation Functions within a Constrained Instanton Model

We suggest a constrained instanton (CI) solution in the physical QCD vacuum which is described by large-scale vacuum field fluctuations. This solution decays exponentially at large distances. It is stable only if the interaction of the instanton with the background vacuum field is small and additional constraints are introduced. The CI solution is explicitly constructed in the ansatz form, and the two-point vacuum correlator of gluon field strengths is calculated in the framework of the effective instanton vacuum model. At small distances the results are qualitatively similar to the single instanton (SI) case, in particular, the form factor $D_{1}$ is small, which is in agreement with the lattice calculations.

hep-ph↗

arXiv1997

Virtualities of Quarks and Gluons in QCD Vacuum and Nonlocal Condensates within Single Instanton Approximation

We calculate the lowest-dimensional nonlocal quark and gluon condensates within the single instanton approximation of the instanton liquid model. As a result, we determine the values of average virtualities of quarks $λ_q^2$ and gluons $λ_g^2$ in the QCD vacuum and obtain parameterless predictions for the ratio $λ_g^2/λ_q^2 = 12/5$, and for some ratios of different vacuum condensates of higher dimensions. The nonlocal properties of quark and gluon condensates are analyzed, and insufficiency of the single instanton approximation is discussed.

hep-ph↗

arXiv1996

Multi-Instanton Effects in QCD Sum Rules for the Pion

Multi-instanton contributions to QCD sum rules for the pion are investigated within a framework which models the QCD vacuum as an instanton liquid. It is shown that in singular gauge the sum of planar diagrams in leading order of the $1/N_{c}$ expansion provides similar results as the effective single-instanton contribution. These effects are also analysed in regular gauge. Our findings confirm that at large distances the correlator functions are more adequately described in the singular gauge rather than in the regular one.

hep-th↗

arXiv1994

Pseudoscalar and vector correlations in instanton vacuum model

It is shown, that the correct account of quark interaction generated by instanton medium gives the possibility of description on the same ground of both pseudoscalar channel and low lying bound states in the vector channel. It must be noted, that all calculations are made in the approximation, taking into account only zero modes.

hep-th↗