Wednesday Colloquium


"Stability-Causality Theorems"

Lorenzo Gavassino (CAMK, Warsaw)

Relativistic hydrodynamics is tricky. There are pitfalls at every corner. Many authoritative textbooks, which are currently used as standard references both in physics and astronomy, present several hydrodynamic equations that lead to completely unphysical predictions (e.g., a glass of water should spontaneously detonate in 10^-34 seconds!). Among such books, we find Novikov-Thorne ("Astrophysics of black holes"), Misner-Thorne-Wheeler ("Gravitation"), Mihalas-Mihalas ("Foundations of radiation hydrodynamics"), and many others. Hence, it is not surprising that such incorrect equations have become part of the "common sense" of a considerable fraction of the astrophysical community, being used both in theoretical models and numerical simulations. How bad is the situation? For decades, some of the brightest minds (e.g. Carter, Israel, Lindblom, Geroch, Anile, Ruggeri) have been looking for more reliable equations, but nobody ever analyzed the problem in full generality. What makes a theory problematic? What makes a theory reliable? What happens if we simulate the wrong theory? Is there an intuitive explanation for all of this? I will provide the definitive answer to all these questions, and I will do it without writing a single equation.



Tomasz Bulik (CAMK, AstroCent, UW, Warsaw)



Francoise Combes