Friedmann Thermodynamics and the Geometry of the Universe
  In a recent article we have introduced Friedmann thermodynamics, where certain geometric parameters in Friedmann models are treated like their thermodynamic counterparts (temperature, entropy, Gibbs potential etc.). This model has the advantage of allowing us to determine the geometry of the universe by thermodynamic stability arguments. In this article we review connections between thermodynamics, geometry and cosmology. 
Selcuk S. Bayin