Kosterlitz-Thouless Transition in the Two-Dimensional Plane Rotator and Coulomb Gas

Abstract
We describe a rigorous argument establishing the Berezinski-Kosterlitz-Thouless transition in a class of two-dimensional models including the plane rotator and the Coulomb gas. The main idea is to rewrite correlations in the Coulomb gas as super-positions of correlations in gases of neutral molecules of variable size and small effective activity.