# The 35th International Symposium on Lattice Field Theory

18-24 June 2017
Palacio de Congresos
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Seminarios 1+2
Chiral Symmetry

# Topology in the chiral symmetry restored phase of unquenched QCD and axion cosmology.

## Speakers

• Prof. Vicente AZCOITI

## Content

The axion is one of the more interesting candidates to make the dark matter of the universe, and the axion potential plays a fundamental role in the determination of the dynamics of the axion field. Moreover, the way in which the $U(1)_A$ anomaly manifests itself in the chiral symmetry restored phase of $QCD$ at high temperature could be tested when probing the $QCD$ phase transition in relativistic heavy ion collisions. With these motivations, we investigate the physical consequences of the survival of the effects of the $U(1)_A$ anomaly in the chiral symmetric phase of $QCD$, and show that the free energy density is a singular function of the quark mass $m$, in the chiral limit, and that the $\sigma$ and $\bar\pi$ susceptibilities diverge in this limit at any $T\ge T_c$. We also show that the difference between the $\bar\pi$ and $\bar\delta$ susceptibilities diverges in the chiral limit at any $T\ge T_c$, a result that can be contrasted with the existing lattice calculations, and discuss on the generalization of these results to the $N_f\ge 3$ model.

Chiral Symmetry