Horizon Chern-Simons Microstates and the Dynamical Origin of Black Hole Entropy and Hawking Radiation

We present a horizon-based framework for black hole thermodynamics whose purpose is not to rederive known entropy formulas, but to explain why black hole entropy and Hawking radiation are unavoidable consequences of quantum gravity. Treating an isolated black hole horizon as an inner boundary of spacetime in first order (Palatini–Holst) gravity, we show that the emergence of a non-gravitational SU(2) Chern–Simons theory on the horizon is a dynamical necessity, rather than an imposed boundary assumption. This follows directly from the reduction of 3 + 1-dimensional gravity to an effective 2+1-dimensional theory on the horizon, togetherwith the absence of local propagating degrees of freedom in 2+1-dimensional gravity. Within this framework, the quantum states of the horizon Chern–Simons theory acquire a clear physical interpretation: each horizon microstate labels a distinct bulk gravitational configuration compatible with the same macroscopic horizon geometry. Black hole entropy thus counts inequivalent interior quantum geometries encoded holographically on the horizon, rather than abstract surface excitations. We further show that Hawking radiation admits a unified statistical-mechanical explanation within this horizon framework. Emission arises from transitions between horizon microstates coupled to matter degrees of freedom, and the thermal character of the radiation follows from detailed balance once the horizon microstates are coarse-grained. Requiring consistency between the microscopic horizon entropy and the universality of the Hawking temperature imposes a nontrivial constraintthat fixes the Immirzi parameter. In this way, black hole entropy and Hawking radiation are shown to originate from the same underlying quantum horizon structure, providing a coherent dynamical and statistical foundation for black hole thermodynamics.