Critical exponents and transport properties near the QCD critical endpoint from the statistical bootstrap model

TL;DR

This paper estimates how shear and bulk viscosities behave near the QCD critical point using the statistical bootstrap model, revealing critical behavior and specific trends in viscosity ratios close to the transition.

Contribution

It provides the first calculation of critical exponents and amplitudes for thermodynamic quantities near the QCD critical point within the statistical bootstrap model.

Findings

Shear viscosity to entropy density ratio decreases and approaches the bound near the critical point.

Bulk viscosity coefficient rises rapidly near the critical point.

Critical exponents for thermodynamic quantities are derived and used to analyze viscosity behavior.

Abstract

We present an estimate of the behaviour of the shear and bulk viscosity coefficients when the QCD critical point is approached from the hadronic side, describing hadronic matter within the statistical bootstrap model (SBM) of strong interactions. The boostrap model shows critical behavior near the quark-hadron transition temperature if the parameter characterizing the degeneracy of Hagedorn states is properly chosen. We calculate the critical exponents and amplitudes of relevant thermodynamic quantities near the QCD critical point and combine them with an Ansatz for the shear and bulk viscosity coefficients to derive the behavior of these coefficients near the critical point. The shear viscosity to entropy density ratio is found to decrease when the temperature is increased, and to approach the Kovtun-Son-Starinets bound 1/(4{\pi}) faster near the critical point, while the bulk viscosity coefficient is found to rise very rapidly.