The magnetized effective QCD phase diagram

TL;DR

This paper investigates how magnetic fields influence the QCD phase diagram using a linear sigma model, revealing inverse magnetic catalysis and shifts in the critical end point due to magnetic effects.

Contribution

It demonstrates the impact of magnetic fields on the QCD phase diagram within a linear sigma model, highlighting inverse magnetic catalysis and the movement of the critical end point.

Findings

Critical temperature decreases with increasing magnetic field.

Critical end point shifts to lower chemical potential and higher temperature.

Magnetic field induces spatial dimension reduction affecting quark interactions.

Abstract

The QCD phase diagram in the temperature versus quark chemical potential plane is studied in the presence of a magnetic field, using the linear sigma model coupled to quarks. It is shown that the decrease of the couplings with increasing field strength obtained in this model leads to the critical temperature for the phase transition to decrease with increasing field intensity (inverse magnetic catalysis). This happens provided that plasma screening is properly accounted for. It is also found that with increasing field strength the location of the critical end point (CEP) in the phase diagram moves toward lower values of the critical quark chemical potential and larger values of the critical temperature. In addition, the CEP approaches the temperature axis for large values of the magnetic field. We argue that a similar behavior is to be expected in QCD, since the physical impact of the magnetic field, regardless of strength, is to produce a spatial dimension reduction, whereby virtual quark-antiquark pairs are closer on average and thus, the strength of their interaction decreases due to asymptotic freedom.