A note on entropy of matter in presence of gravity: status of extensivity of entropy

Abstract

Entropy of matter in a very strong gravity depends on cross-sectional area of the container of the system -- is being further bolstered by calculating entropy of a monoatomic gas kept under uniform strong gravity at Newtonian scale. This bypasses the earlier analysis where existence of horizon is crucial. Also the extensivity of this entropy has been discussed in the light of the same of a two-space dimensional ultra-relativistic non-interacting gas without gravity. The whole analysis, as far as entropy is concerned, indicates that under strong gravity the microscopic degrees of freedom of the system are effectively contributed by the cross-sectional area of the system.