A recent theoretical work has developed an on-shell framework to describe thermal dissipation and radiation by macroscopic objects, including black holes. This novel approach represents equilibrium asymptotic states as on-shell particles and non-equilibrium processes through on-shell transition amplitudes between them. The key insight is that the large degeneracy of internal states of these objects is encoded in their entropy, allowing for a unified description of thermal phenomena.

A central observation of the study is the importance of spinning states, even for macroscopically non-rotating objects. Consistency with macroscopic symmetries leads to spin universality, implying that all spinning states are governed by a single universal coupling. This universality has a crucial consequence: absorption and emission probabilities are controlled by the same coupling, allowing for the derivation of local detailed balance directly from on-shell data.

Applied to black holes, this framework reproduces the thermal emission spectrum of Hawking radiation. Furthermore, it establishes a fundamental connection between the Hawking temperature and the condition of maximal absorption, which in turn is consistent with unitary time evolution. This result is significant as it offers a new perspective on black hole thermodynamics, integrating it with concepts from quantum field theory and particle physics.

The development of this on-shell framework opens avenues for a deeper understanding of the interplay between gravity, thermodynamics, and quantum mechanics in the context of compact objects. It could lay the groundwork for future investigations into black hole information and the fundamental nature of spacetime, by providing a unified tool to analyze these complex phenomena.