Thermodynamics of the two-dimensional XY model from functional renormalization

Understand

We solve the nonperturbative renormalization-group flow equations for the two-dimensional XY model at the truncation level of the (complete) second-order derivative expansion.

• We compute the thermodynamic properties in the high-temperature phase and compare the non-universal features specific to the XY model with results from Monte Carlo simulations.
• In particular, we study the position and magnitude of the specific heat peak as a function of temperature.
• The obtained results compare well with Monte Carlo simulations.