Parikh, MaulikMaulikParikhSarkar, SudiptaSudiptaSarkarSvesko, AndrewAndrewSvesko2025-08-312025-08-312020-05-1510.1103/PhysRevD.101.1040432-s2.0-85086000637https://d8.irins.org/handle/IITG2025/24150We find a (quasi)local first law of thermodynamics, ΔE=TΔS-W, connecting gravitational entropy, S, with matter energy and work. For Einstein gravity, S is the Bekenstein-Hawking entropy, while for general theories of gravity, S is the Wald entropy, evaluated on the stretched future light cone of any point in an arbitrary spacetime, not necessarily containing a black hole. The equation can be written as ρΔV=TΔS-pΔV by regarding the energy-momentum tensor as that of a fluid.falseArticlehttps://arxiv.org/pdf/1801.073062470002915 May 20205104043arJournal5WOS:000535454600011