Critical Slowing Down and Bulk Viscosity in Binary Neutron Star Mergers with Rachel Steinhorst

Near the critical endpoint of a first order phase transition, the relaxation time diverges, the well-known phenomenon of critical slowing down. One manifestation of critical slowing down is a divergence of the bulk viscous transport coefficient. Although a QCD critical point is traditionally imagined to be at high temperatures, no first-principles argument forbids a QCD critical point in the low-temperature phase space probed by binary neutron star mergers. We perform an order of magnitude estimation for the enhancement of the neutron star bulk viscosity due to such a critical point, and find that it can under some circumstances far exceed the viscous effect of beta equilibration in matter sufficiently close to the critical point.

This lecture was made possible by the William C. Ferguson Fund.