Speaker
Description
Heavy-ion collision experiments have provided compelling evidence that quarks and gluons can behave as a strongly interacting, low-viscosity relativistic liquid over distance scales not much larger than the size of a proton. Meanwhile, gravitational-wave observations of binary neutron star mergers have made understanding the dynamics of extremely dense matter in strong gravitational fields increasingly urgent. These systems probe vastly different scales, yet both challenge our understanding of when relativistic fluid dynamics applies and how to formulate its equations consistently.
In this talk, I will describe recent developments in our understanding of the onset of relativistic fluid behavior and its applicability far from equilibrium. I will present rigorous results that, under explicit conditions, establish causality and local well-posedness for two major frameworks of relativistic viscous fluid dynamics coupled to Einstein’s equations: Israel–Stewart theory and the Bemfica–Disconzi–Noronha–Kovtun formalism. I will discuss open questions concerning the physical and mathematical properties of relativistic viscous fluids dynamically coupled to strong electromagnetic and gravitational fields. Finally, I will examine whether, and under what conditions, the breakdown of fluid evolution is related to geodesic incompleteness, and what this connection could teach us about black hole formation in neutron star mergers.