Dual Affine Connections, Legendre Transforms, and Black Hole Thermodynamics

Abstract

Geometrical methods have become increasingly important in understanding both thermodynamics and information theory. In particular, dual affine (Hessian) geometry offers a powerful unification of concepts by recasting Legendre transformations as coordinate changes on a manifold endowed with a strictly convex potential. This viewpoint illuminates the mathematical basis of key thermodynamic relations, such as the mappings between internal energy U(S,V) and other potentials like Helmholtz or Gibbs free energies, and connects these ideas to the broader framework of information geometry, where dual coordinate systems naturally arise. In this paper, we present a concise treatment of how dual affine connections $(\nabla, \nabla^*)$ emerge from a single convex potential and are directly related through Legendre transforms. This emphasizes their physical significance and the geometric interpretation of entropy maximization. We then explore an energy gap integral constructed from the cubic form of the Hessian metric that measures how far a system deviates from the Levi Civita connection a self dual connection, and discuss how quantum-scale effects may render this gap infinite below the Planck length. Finally, we apply these concepts to black hole thermodynamics, showing how quantum or measurement uncertainties in (T,S,F,U) can be incorporated into the Hessian framework and interpreted via Hawking radiation in a stable black hole scenario. This unifying perspective underscores the natural extension from classical Riemannian geometry to dual-affine thermodynamics, with potential ramifications for quantum gravity and advanced thermodynamic modeling.