Thermodynamic instability of de Sitter space

The generalized second law of thermodynamics is applied to fluctuations in the Hawking temperature of the cosmological event horizon in de Sitter spacetime. Fluctuations which decrease the temperature, thereby decreasing the scalar curvature, increase the generalized entropy S. Thus, the generalized second law implies that de Sitter space is unstable to fluctuations which decrease the effective cosmological constant.