Date: 25 September 2026, Friday
Time: 15:30
Place: SA-240
Shahin Sheikh-Jabbari
IPM Tehran
“Entropy and the second law of thermodynamics in gravitating systems”
Abstract
It is well established that black holes possess entropy and behave as thermodynamic systems. Associating entropy with gravitational fields has not remained limited to black holes, necessitating the notion of the second law of thermodynamics in gravitating systems. There have been many ideas and attempts to prove the second law within gravitating systems starting from first principles. Within the covariant phase space formalism, we define gravitational entropy as the charge associated with the local boosts, detaching the gravitational entropy from horizons or trapped surfaces as well as from the diffeomorphisms as symmetry generators. Using this definition for the Einstein gravity case, we compute variations of the entropy along the path of any causal free-fall observer and establish that the entropy variations are always non-negative if the matter content satisfies the strong energy condition integrated along any segment of the observer’s trajectory.
Mohammad Mahdi Sheikh-Jabbari (Shahin Sheikh-Jabbari) is a Professor of Physics at IPM Tehran, a position he has held since 2006. He earned his PhD from Sharif University in Tehran in 1998, and after seven years of postdoctoral research at IPM, ICTP Trieste, and Stanford University, he joined IPM in 2005. His research focuses on theoretical high-energy physics and cosmology, particularly black hole physics and late-time cosmology. In 2022, he coauthored the graduate textbook Black Holes, from collapse to evaporation, published by Springer.