Confining and chiral properties of QCD in extremely strong magnetic fields

TL;DR

This study uses lattice QCD simulations to explore how extremely strong magnetic fields affect confinement and chiral symmetry, revealing significant anisotropic modifications to the quark-antiquark potential and evidence of magnetic catalysis.

Contribution

It provides the first continuum-extrapolated results on the impact of magnetic fields up to 9 GeV² on QCD confinement and chiral properties with physical quark masses.

Findings

Longitudinal string tension is suppressed by an order of magnitude at high magnetic fields.

Transverse string tension is enhanced but saturates at about 50% of its zero-field value.

Chiral condensate increases linearly with magnetic field, indicating magnetic catalysis.

Abstract

We investigate, by numerical lattice simulations, the static quark-antiquark potential, the flux tube properties and the chiral condensate for $N_f = 2+1$ QCD with physical quark masses in the presence of strong magnetic fields, going up to $eB = 9$ GeV$^2$, with continuum extrapolated results. The string tension for quark-antiquark separations longitudinal to the magnetic field is suppressed by one order of magnitude at the largest explored magnetic field with respect to its value at zero magnetic background, but is still non-vanishing; in the transverse direction, instead, the string tension is enhanced but seems to reach a saturation at around 50 % of its value at $B = 0$. The flux tube shows a consistent suppression/enhancement of the overall amplitude, with mild modifications of its profile. Finally, we observe magnetic catalysis in the whole range of explored fields with a behavior compatible with a lowest Landau level approximation, in particular with a linear dependence of the chiral condensate on $B$ which is in agreement, within errors, with that already observed for $eB \sim 1$ GeV$^2$.