Universality driven analytic structure of the QCD crossover: radius of convergence in the baryon chemical potential

TL;DR

This paper explores the universal analytic structure of the QCD crossover, using lattice QCD results to determine the radius of convergence in baryon chemical potential and its implications for the QCD critical point.

Contribution

It introduces a universal analysis of the QCD crossover's analytic structure and maps the singularity to constrain the validity range of lattice QCD at finite chemical potential.

Findings

Identifies the Yang-Lee edge singularity in QCD crossover.

Maps the singularity to the complex 1 plane using lattice results.

Provides bounds on the applicability of lattice QCD at finite 1.

Abstract

Recent lattice QCD calculations strongly indicate that the chiral crossover of QCD at zero baryon chemical potential \mu_B is a remnant of the second-order chiral phase transition. Universal properties of this second-order phase transition can be mapped to QCD temperature T and \mu_B using non-universal parameters determined by lattice QCD recently. Motivated by these results, first, we discuss the analytic structure of the partition function in the QCD crossover regime - the so-called Yang-Lee edge singularity - solely based on universal properties. Next, utilizing the lattice QCD results for non-universal parameters we map this singularity to the real T and complex \mu_B plane, leading to the determination of the radius of convergence is in \mu_B in the QCD crossover regime. These universality- and QCD-based results provide tight constraints on the range of validity of the lattice QCD calculations at \mu_B. Implication of this result on the location of the conjectured QCD critical point is discussed.