Renormalization Group Flow Equations and the Phase Transition in   O(N)-models
  We derive and solve flow equations for a general O(N)-symmetric effective potential including wavefunction renormalization corrections combined with a heat-kernel regularization. We investigate the model at finite temperature and study the nature of the phase transition in detail. Beta functions, fixed points and critical exponents \beta, \nu, \delta and \eta for various N are independently calculated which allow for a verification of universal scaling relations. 
O. Bohr, B.-J. Schaefer, J. Wambach (TU Darmstadt)