Critical behavior of three-dimensional magnets with complicated ordering   from three-loop renormalization-group expansions
  The critical behavior of a model describing phase transitions in 3D antiferromagnets with 2N-component real order parameters is studied within the renormalization-group (RG) approach. The RG functions are calculated in the three-loop order and resummed by the generalized Pade-Borel procedure preserving the specific symmetry properties of the model. An anisotropic stable fixed point is found to exist in the RG flow diagram for N > 1 and lies near the Bose fixed point; corresponding critical exponents are close to those of the XY model. The accuracy of the results obtained is discussed and estimated. 
A. I. Sokolov and K. B. Varnashev (Saint Petersburg Electrotechnical   University, St.Petersburg, Russia)