Regular Article - Theoretical Physics
The P-V phase transition of the FRW universe
College of Physics, Nanjing University of Aeronautics and Astronautics, 211106, Nanjing, China
2 School of Physics and Technology, University of Jinan, 336 West Road of Nan Xinzhuang, 250022, Jinan, Shandong, China
3 Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100190, Beijing, China
4 Key Laboratory of Aerospace Information Materials and Physics (NUAA), MIIT, 211106, Nanjing, China
Accepted: 29 October 2022
Published online: 18 November 2022
We define thermodynamic pressure P by work density W as the conjugate quantity of thermodynamic volume V from field equation. We derive the equations of state P=P(V, T) for the Friedmann–Robertson–Walker (FRW) universe in Einstein gravity and a modified gravity respectively. We find that the equation of state from Einstein gravity shows no P-V phase transition, while the equation of state from the modified gravity does, where the critical exponents are the same as those in mean field theory.
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