Main field of study: 011200 Physics
Area of specialization: Theory of Elementary Particle Interaction and Quantum Field Theory
Department of High Energy and Elementary Particle Physics 
Scientific advisor: Prof. Dr. N.V. Antonov
Reviewer: Prof. Dr. L. Ts. Adzhemyan

Critical behavior of the systems with a tensor order parameter: Three-loop approximation
Lebedev Nikita

Numerous physical systems reveal interesting singular behavior in the vicinity of their critical points. Their thermodynamical and correlation functions exhibit scaling behavior with universal critical dimensions: according to general belief, they depend only on a few global characteristics of the system, such as symmetry or dimension.
The main purpose of this work was to study the critical behavior of the rotationally symmetric system of the real tensor order parameter with quartic interaction.
In order to achieve the formulated goal RG-functions of the model were calculated in three-loop approximation. The critical exponents were presented in the form of series expansion by the deviation of the spatial dimension from its logarithmic value in same approximation. In order to obtain the numerical values of the critical exponents at physical value of spatial dimension the asymptotic of  high orders of perturbation theory was studied. Final results were obtained by resummation of previously calculated segments of the series expansions by method of conformal transformation of Borel.

The list of publications:
1.	N V Antonov, M V Kompaniets and N M Lebedev, Critical behaviour of the O(n)-φ4 model with an antisymmetric tensor order parameter, J. Phys. A: Math. Theor. 46 (2013) 405002
2.	Lebedev N, Critical behavior of the O(n)-φ4 model with an antisymmetric tensor order parameter; Science and Progres- 2013, St. Petersburg – Peterhof.