Radiation Entropy Bound from the Second Law of Thermodynamics

Itzhak Fouxon

doi:10.3390/e14040736

Abstract

It has been suggested heuristically by Unruh and Wald, and independently by Page, that at given energy and volume, thermal radiation has the largest entropy. The suggestion leads to the corresponding universal bound on entropy of physical systems. Using a gedanken experiment we show that the bound follows from the Second Law of Thermodynamics if the CPT symmetry is assumed and a general condition on matter holds. The experiment suggests that a wide class of Lorentz invariant local quantum field theories obeys a bound on the density of states.

Highlights

The demand that total entropy of a closed system never decreases imposes important constraints on the structure of microscopic theories
The bound is based upon the demand that the total entropy never decreases in gedanken experiments that involve a macroscopic system absorption by a black hole
The derivation employs an extended version of the second law that includes the contribution of the black holes in the total entropy

Summary

Introduction

The demand that total entropy of a closed system never decreases imposes important constraints on the structure of microscopic theories. Using that any physical system interacts with a black hole, Bekenstein proposed a universal entropy bound for the entropy of weakly gravitating systems: The bound is based upon the demand that the total entropy never decreases in gedanken experiments that involve a macroscopic system absorption by a black hole.

Results

Conclusion