Constraints on the Value of the Fine Structure Constant from Gravitational Thermodynamics

In this paper I show how the second law of thermodynamics, generalized to include event horizon area, places interesting constraints on the value of the fine structure constant α. A simple analysis leads to the approximate constraint α<1, although I suggest ways in which this bound might be reduced by a more detailed calculation. The analysis also leads to the conclusion that the existence of classical Dirac and point-like magnetic monopoles are inconsistent with the second law, and that GUT monopoles are inconsistent with either the second law or the existence of minicharged particles.