On dissipation in relativistic fluid theories

Fluid mechanics has proven to be remarkably successful in describing a wide variety of substances, both familiar and exotic. The latter category includes relativistic fluids, often arising in the most extreme regimes found anywhere in the universe. One such example is the quark-gluon plasma (QGP) formed in collisions of heavy ions, which exists at temperatures hot enough to “melt” hadrons; another is the matter composing neutron stars, whose density is comparable to that of an atomic nucleus. Beyond the surprising fact that the aforementioned substances act as fluids, they share an additional similarity in that they may both be measurably viscous, a feature accounted for in models of the QGP but almost never in neutron star simulations.

In this talk I will overview progress toward the incorporation of dissipative effects such as viscosity into relativistic fluid models of astrophysical systems. I will begin by reviewing the modern inter- pretation of fluid mechanics as a gradient expansion about thermodynamic equilibrium, and will discuss the nuances of constructing a theory compatible with beyond-equilibrium thermodynamics and general relativity. I will then define and motivate a promising new formulation of relativistic dissipative hydrodynamics known as BDNK theory before summarizing recent work toward its application in models of neutron stars.

Zoom link:  https://pitp.zoom.us/j/99927210105?pwd=aUJWa0NobWFrT0FHMUhqZmRHWlREdz09