Real time warm pions from the lattice using an effective theory

TL;DR

This paper demonstrates how lattice data can be used with effective field theories to analytically continue pion correlation functions from Euclidean to Minkowski space, revealing insights into long-distance excitations at high temperatures.

Contribution

It provides a method to perform analytic continuation of lattice-derived correlation functions, showing that long-distance pion excitations persist above the QCD crossover temperature.

Findings

Analytic continuation of pion correlators is feasible and reveals non-trivial effects.

Long-distance excitations at high temperature can be described by massive pions.

Supports the idea that pions influence the quark-gluon plasma even above the crossover temperature.

Abstract

Lattice measurements provide adequate information to fix the parameters of long distance effective field theories in Euclidean time. Using such a theory, we examine the analytic continuation of long distance correlation functions of composite operators at finite temperature from Euclidean to Minkowski space time. We show through an explicit computation that the analytic continuation of the pion correlation function is possible and gives rise to non-trivial effects. Among them is the possibility, supported by lattice computations of Euclidean correlators, that long distance excitations can be understood in terms of (very massive) pions even at temperatures higher than the QCD cross over temperature.