# Temperature effect on shear and bulk viscosities of QCD matter

Gao, Fei (Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China) (Collaborative Innovation Center of Quantum Matter, Beijing 100871, China) ; Liu, Yu-xin (Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China) (Collaborative Innovation Center of Quantum Matter, Beijing 100871, China) (Center for High Energy Physics, Peking University, Beijing 100871, China)

15 March 2018

Abstract: With developing a scheme to determine the thermal width of a pion in a medium, we investigate the shear and bulk viscosities and their ratios to entropy density. We calculate the temperature ($T$)-dependence of the pion mass and decay constant via the Dyson-Schwinger equations of QCD and get the pion thermal width with the QCD approach. We obtain then the $T$-dependence of the viscosities, especially a novel feature of the bulk viscosity, via the continuum QCD approach. The novel concavo-convex behavior of the bulk viscosity to entropy density ratio against the temperature is a demonstration of the QCD phase transitions.

Published in: Phys. Rev. D 97 (2018)