English

Arrow of time and gravitational entropy in collapse

General Relativity and Quantum Cosmology 2025-08-11 v2 High Energy Physics - Theory

Abstract

We investigate the status of the gravitational arrow of time in the case of a spherical collapse of a fluid that conducts heat and radiates energy. In particular, we examine the results obtained by W. B. Bonnor in his 1985 paper where he found that the gravitational arrow of time was opposite to the thermodynamic arrow of time. The measure of gravitational epoch function PP used by Bonnor was given by the ratio of the Weyl square to the Ricci square. In this paper, we have assumed the measure of gravitational entropy P1P_{1} to be given by the ratio of the Weyl scalar to the Kretschmann scalar. Our analysis indicates that Bonnor's result seems to be validated, i.e., the gravitational arrow and the thermodynamic arrow of time point in opposite directions. This strengthens the opinion that the Weyl proposal of gravitational entropy applies only to the universe as a whole (provided that we exclude the white holes).

Keywords

Cite

@article{arxiv.2402.04188,
  title  = {Arrow of time and gravitational entropy in collapse},
  author = {Samarjit Chakraborty and Sunil D. Maharaj and Sarbari Guha and Rituparno Goswami},
  journal= {arXiv preprint arXiv:2402.04188},
  year   = {2025}
}

Comments

19 pages, accepted for publication in CQG