Three very different universes share identical thermodynamic laws

Treating gravity as just another matter field, Volovik works out the thermodynamics of three toy universes — one driven by vacuum energy, one by a magnetic field, one by ordinary matter — and finds all three obey exactly the same thermodynamic equation. As a bonus, in empty Minkowski space the framework automatically sets the cosmological constant to zero. The result hints that deep thermodynamic structure may be independent of what actually fills a universe.