Strongly coupled matter near phase transition

TL;DR

This paper investigates the transport properties of strongly coupled scalar matter near phase transition using the CJT formalism, revealing small shear viscosity, large bulk viscosity, and significant deviations from conformality, consistent with lattice QCD results.

Contribution

It provides a theoretical analysis of viscosities and conformality deviations in strongly coupled scalar systems near phase transition within the CJT framework.

Findings

Shear viscosity over entropy density is small near phase transition.

Bulk viscosity over entropy density is large near phase transition.

Square of the sound velocity is much smaller than 1/3 near phase transition.

Abstract

In the Hartree approximation of Cornwall-Jackiw-Tomboulis (CJT) formalism of the real scalar field theory, we show that for the strongly coupled scalar system near phase transition, the shear viscosity over entropy density is small, however, the bulk viscosity over entropy density is large. The large bulk viscosity is related to the highly nonconformal equation of state. It is found that the square of the sound velocity near phase transition is much smaller than the conformal value 1/3, and the trace anomaly at phase transition deviates far away from 0. These results agree well with the lattice results of the complex QCD system near phase transition.