Stephen Hawking studied how gravitation and quantum physics change thermal equilibrium. In his 1983 collaboration with Don N. Page, a negative cosmological constant altered the temperature–size relation of a black hole, permitting a large positive-heat capacity branch in Anti-de Sitter spacetime.[ref]
Thermodynamics of black holes in anti-de Sitter space by Stephen Hawking and Don N. Page. Sections 2–3: Euclidean temperature and canonical thermodynamics
This provided a concrete phase transition problem in black-hole thermodynamics, comparing the free energies of black-hole and thermal-radiation configurations under the same boundary conditions.
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Stephen Hawking was a renowned theoretical physicist, cosmologist, and author, best known for his work on black holes, the nature of the universe, and concepts like Hawking radiation. Born on January 8, 1942, in Oxford, England, he had a distinguished academic career, earning his PhD from the University of Cambridge.
While learning black-hole stuff is not on top of Ciro Santilli's priorities, Hawking's spirit is to be admired.
An ex-physicist colleague who had met Hawking told an anecdote. Hawking was around in the department one day, they said hi and all. But then Hawking wanted to tell a joke. It took like 5 minutes of typing, and you can imagine that things were pretty awkward and the joke's timing was "a bit off". But Hawking did tell the joke nonetheless.
This is also suggested in the The Theory of Everything (2014) film, and therefore likely the biographies.