Thermal QCD in a non-uniform magnetic background

TL;DR

This study uses lattice QCD simulations with inhomogeneous magnetic fields to explore how such fields affect the QCD medium, revealing non-trivial spatial features and guiding effective theory development.

Contribution

It provides the first lattice QCD analysis of inhomogeneous magnetic fields, comparing results with chiral perturbation theory and enhancing understanding of magnetic effects in heavy-ion collisions.

Findings

Magnetic fields induce non-trivial spatial features in the QCD medium.

Results differ significantly from homogeneous magnetic field cases.

Findings help benchmark effective theories for peripheral heavy-ion collisions.

Abstract

Off-central heavy-ion collisions are known to feature magnetic fields with magnitudes and characteristic gradients corresponding to the scale of the strong interactions. In this work, we employ equilibrium lattice simulations of the underlying theory, QCD, involving similar inhomogeneous magnetic field profiles to achieve a better understanding of this system. We simulate three flavors of dynamical staggered quarks with physical masses at a range of magnetic fields and temperatures, and extrapolate the results to the continuum limit. Analyzing the impact of the field on the quark condensate and the Polyakov loop, we find non-trivial spatial features that render the QCD medium qualitatively different as in the homogeneous setup, especially at temperatures around the transition. In addition, we construct leading-order chiral perturbation theory for the inhomogeneous background and compare its prediction to our lattice results at low temperature. Our findings will be useful to benchmark effective theories and low-energy models of QCD for a better description of peripheral heavy-ion collisions.