Generalised focusing theorem and dynamical horizon entropy in diffeomorphism-invariant theories
Abstract
Abstract I summarise recent progress on light-ray focusing and horizon thermodynamics in general diffeomorphism-invariant theories of gravity coupled to bosonic matter. In pure gravity and with scalar or vector fields, the null-null gravitational equation of motion on a linearly perturbed Killing horizon generalises the Raychaudhuri equation, defining a generalised expansion that never increases under the null energy condition. This proves a generalised focusing theorem and defines an increasing horizon entropy (Wall entropy). When higher-spin fields are present, the generalised focusing theorem persists subject to a “higher-spin focusing condition”, which I propose as a physical consistency constraint on higher-spin theories.
Fields of Study & Subjects
Cosmology and Gravitation Theories
Black Holes and Theoretical Physics
Noncommutative and Quantum Gravity Theories
Publication details
- Journal / source
- Journal of Physics Conference Series
- Publisher
- IOP Publishing
- Volume
- 3177
- Issue
- 1
- Pages
- 012032–012032
- Publication date
- 1 February 2026