Nonperturbative renormalization flow and essential scaling for the Kosterlitz-Thouless transition - art. no. 054513

The Kosterlitz-Thouless phase transition is described by the nonperturbativ e renormalization flow of the two-dimensional phi (4) model. The observatio n of essential scaling demonstrates that the flow equation incorporates non perturbative effects that have previously found an alternative description in terms of vortices. The duality between the linear and nonlinear sigma mo del gives a unified description of the long-distance behavior for O(N) mode ls in arbitrary dimension d. We compute critical exponents in first order i n the derivative expansion.