Effects of low-lying fermion modes in the epsilon regime

TL;DR

This paper studies how low-lying fermion modes influence the QCD partition function in the epsilon-regime, using lattice calculations and comparing results with theoretical predictions.

Contribution

It introduces a method to incorporate low-lying fermion modes into the QCD partition function using the truncated determinant approximation.

Findings

Agreement with Leutwyler and Smilga's theoretical predictions

Demonstrates the effectiveness of the truncated determinant approximation

Provides insights into fermion effects in the epsilon-regime

Abstract

We investigate the effects of low-lying fermion modes on the QCD partition function in the epsilon-regime. With the overlap Dirac operator we calculate several tens of low-lying fermion eigenvalues on the quenched lattice. By partially incorporating the fermion determinant through the truncated determinant approximation, we calculate the partition function and other related quantities for Nf = 1 and compare them with the theoretical predictions obtained by Leutwyler and Smilga.