Phase transitions and critical phenomena for the FRW universe in an effective scalar-tensor theory

• DOI: 10.1016/j.dark.2023.101330
• Publication Date: 2023-09-22T16:29:40Z
• Authors: Haximjan Abdusattar; Shi-Bei Kong; Hongsheng Zhang; Ya-Peng Hu
• Keywords: Friedmann–Lemaître–Robertson–Walker metric

12 pages, 1 figures<br/>We find phase transitions and critical phenomena of the FRW (Friedmann-Robertson-Walker) universe in the framework of an effective scalar-tensor theory that belongs to the Horndeski class. We identify the thermodynamic pressure (generalized force) $P$ of the FRW universe in this theory with the work density $W$ of the perfect fluid, which is a natural definition directly read out from the first law of thermodynamics. We derive the thermodynamic equation of state $P=P(V, T)$ for the FRW universe in this theory and make a thorough discussion of its $P$-$V$ phase transitions and critical phenomena. We calculate the critical exponents, and show that they are the same with the mean field theory, and thus obey the scaling laws.<br/>