title: Berezinskii-Kosterlitz-Thouless phase transitions in two-dimensional non-Abelian spin models.
abstract: It is argued that two-dimensional U(N) spin models for any N undergo a Berezinskii-Kosterlitz-Thouless (BKT)-like phase transition, similarly to the famous XY model. This conclusion follows from the Berezinskii-like calculation of the two-point correlation function in U(N) models, approximate renormalization group analysis, and numerical investigations of the U(2) model. It is shown, via Monte Carlo simulations, that the universality class of the U(2) model coincides with that of the XY model. Moreover, preliminary numerical results point out that two-dimensional SU(N) spin models with the fundamental and adjoint terms and N>4 exhibit two phase transitions of BKT type, similarly to Z(N) vector models.
authors: Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 03680 Kiev, Ukraine.
authors: Oleg
authors: O
authors: Borisenko
authors: Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 03680 Kiev, Ukraine.
authors: Volodymyr
authors: V
authors: Chelnokov
authors: Dipartimento di Fisica dell'Università della Calabria, I-87036 Arcavacata di Rende, Cosenza, Italy and INFN-Gruppo collegato di Cosenza, I-87036 Arcavacata di Rende, Cosenza, Italy.
authors: Francesca
authors: F
authors: Cuteri
authors: Dipartimento di Fisica dell'Università della Calabria, I-87036 Arcavacata di Rende, Cosenza, Italy and INFN-Gruppo collegato di Cosenza, I-87036 Arcavacata di Rende, Cosenza, Italy.
authors: Alessandro
authors: A
authors: Papa