The Stability-Causality Theorem

Special relativity is counterintuitive. More than a century after its discovery, it still seems to have some surprises in store for us. In this talk, I will present a new theorem, which states that thermodynamic irreversibility is compatible with special relativity if and only if the principle of causality holds (i.e. information cannot travel faster than light). This fundamental result finally explains why so many relativistic hydrodynamic theories happen to be unstable, and it can be used as a guiding principle in the search for reliable fluid theories.