Inflationary QCD phase diagram

TL;DR

This paper explores the phase diagram of multi-flavor QCD in de Sitter space during inflation, revealing conditions for a first-order chiral phase transition driven by an axial chemical potential, with implications for cosmological collider physics.

Contribution

It introduces a novel analysis of the QCD phase diagram in de Sitter spacetime using an effective NJL model, connecting cosmological inflation to QCD phase transitions.

Findings

Identification of the first-order critical line and critical point in the QCD phase diagram during inflation.

Demonstration that a first-order chiral phase transition can occur during or after inflation.

Establishment of a cosmological collider analogue of the QCD phase diagram.

Abstract

Motivated by the cosmological collider program, which aims to probe high-energy physics through inflation, we investigate the phase diagram of multi-flavor QCD in de Sitter spacetime with a flavor-universal axial chemical potential induced by a rolling inflaton coupled to fermions. We determine the first-order critical line and a critical point as functions of the Hubble parameter and the axial chemical potential, employing an effective description of chiral symmetry breaking within the framework of the Nambu--Jona-Lasinio model. We find that a first-order chiral phase transition may occur during inflation or at its end when the axial chemical potential is sufficiently large and crosses the critical line. This provides a cosmological collider analogue of the QCD phase diagram explored in heavy-ion colliders.