Lattice versus 2PI: 2d O(N) model at nonzero T

TL;DR

This paper compares the thermodynamics of the 1+1 dimensional O(N) model using the CJT formalism, auxiliary field method, and lattice simulations, finding good agreement at two-loop order.

Contribution

It provides a detailed comparison between the CJT formalism and lattice simulations for the 2D O(N) model at finite temperature, highlighting the effectiveness of the two-loop approximation.

Findings

Good correspondence between CJT and lattice results at two-loop order.

Renormalized mass, pressure, and trace anomaly are accurately computed.

Two-loop CJT formalism effectively captures the thermodynamics of the model.

Abstract

The thermodynamics of the O(N) model in 1+1 dimensions is studied applying the CJT formalism and the auxiliary field method as well as fully nonperturbative finite temperature lattice simulations. The numerical results for the renormalized mass of the scalar particles, the pressure and the trace anomaly are presented and compared with the results from lattice simulation of the model. We find that when going to the two loop order we observe a good correspondence between the CJT formalism and the lattice study.