Speaker
Description
Estimating the value of bulk viscosity in neutron stars is crucial to determine the dampening of oscillations and gravitational wave emission in pulsars and binary mergers. The main contribution originates from weak processes through beta equilibration rates and depends both on the equation of state and weak equilibration rates. We use symmetry arguments in the form of Ward identities to derive general formulas for weak equilibration rates in terms of spectral functions of flavor currents. We then apply the general formulas to obtain the temperature dependence of weak rates and the bulk viscosity in strongly coupled quark matter using a holographic model. We compare the values obtained from the holographic model with perturbative estimates and with the bulk viscosity of pure QCD contribution at strong coupling.
