Dr Lorenzo Gavassino

Dr Lorenzo Gavassino received his Master’s degree (cum laude) in Physics from the University of Milano “La Statale” in Milan, Italy, and moved to the Nicolaus Copernicus Astronomical Center of the Polish Academy of Science in Warsaw, Poland, for his doctoral studies (initially with a Della Riccia fellowship). He graduated in June 2022 and obtained his PhD (with distinction) in astronomy and
astrophysics with a thesis on “Thermodynamic methods for relativistic hydrodynamics”. He is currently a postdoctoral scholar at the department of mathematics of Vanderbilt University, in Nashville, USA, and member of the Vanderbilt Initiative for Gravity, Waves, and Fluids (VandyGRAF).

Dr Gavassino’s thesis focuses on how to develop a formulation of viscous hydrodynamics in general relativity. The topic has become of importance for multi-messenger astronomy, given the detection of gravitational waves created during the final stages of inspiral and coalescence of two neutron stars (GW170817A). Events like this are very energetic and require the use of relativistic, dissipative fluid dynamics for modeling and data extraction. However, the theoretical foundations of relativistic dissipative fluid dynamics are not completely settled, with troubling issues dealing with causality and stability still unresolved.

His work approaches these issues of causality and stability in a modern and original way,namely, to start the discussion of a many-particle system with well-established conservation rules, such as energy, mass, and momentum, to build a manifold of possible thermodynamic states. Dr Gavassino clarified several outstanding questions concerning the role played by the second law of thermodynamics in the determination of the stability properties of relativistic fluids. He explained why the fluid dynamic formulations are inconsistent with relativity, even though they formally satisfy the second law of thermodynamics. Furthermore, he created a quick systematic technique to construct a quadratic Lyapunov-like functional that can be used to investigate the stability properties of relativistic viscous fluid dynamic theories with an entropy current that exactly satisfies the second law of thermodynamics. His work provided for the first time both a systematic method for constructing such a functional and also the physics reasoning behind it. In a separate paper, he showed that relativistic fluids, which possess a well-defined entropy current that is maximized in
equilibrium according to the second law of thermodynamics, cannot possess superluminal perturbations that would violate relativistic causality. The PhD thesis of Dr Lorenzo Gavassino was conducted at the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences in Warsaw, Poland, under the supervision of Professor Brynmor Haskell.