Topological and optical signatures of modified black-hole entropies
arXiv:2512.13769 · doi:10.1140/epjc/s10052-026-15365-0
Abstract
We investigate how deviations from the Bekenstein-Hawking entropy modify black-hole spacetimes through the recently proposed entropy-geometry correspondence. For four representative modified entropies, namely Barrow, Rényi, Kaniadakis, and logarithmic, we derive the corresponding effective metrics and analyze their thermodynamic and topological classification using the off-shell free energy and winding numbers. We show that Barrow and Rényi entropies yield a single unstable sector with global charge , while logarithmic and Kaniadakis corrections produce canceling defects with , revealing topological structures absent in the Schwarzschild case. Using the modified metrics, we further calculate the photon-sphere radius and shadow size, showing that each modified entropy relation induces characteristic optical shifts. Thus, by comparing with Event Horizon Telescope observations of Sgr A, we extract new bounds on all entropy-deformation parameters. Our results demonstrate that thermodynamic topology, together with photon-sphere phenomenology, offers a viable way to test generalized entropy frameworks and probe departures from the Bekenstein-Hawking area law.
15 pages, 9 figures
References in corpus (38)
- Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A
- Black Hole Solutions as Topological Thermodynamic Defects
- Modified cosmology from extended entropy with varying exponent
- Early and late universe holographic cosmology from a new generalized entropy
- Modified cosmology through spacetime thermodynamics and Barrow horizon entropy
- Exponential corrections to black hole entropy
- Universal topological classifications of black hole thermodynamics
- New entropies, black holes, and holographic dark energy
- Baryogenesis in non-extensive Tsallis Cosmology
- Alleviating both and tensions in Tsallis cosmology
- Geometric Approach to Circular Photon Orbits and Black Hole Shadows
- Entropic corrections to Friedmann equations and bouncing universe due to the zero-point length
- Tsallis cosmology and its applications in dark matter physics with focus on IceCube high-energy neutrino data
- Black hole geometrothermodynamics and critical phenomena: a look from Tsallis entropy-based perspective
- Curvatures, Photon Spheres and Black Hole Shadows
- Tsallis holographic dark energy for inflation
- Imprints of Barrow-Tsallis Cosmology in Primordial Gravitational Waves
- Constraints on Tsallis Cosmology from Big Bang Nucleosynthesis and the Relic Abundance of Cold Dark Matter Particles
- Modified Cosmology Models from Thermodynamical Approach
- Fractional Holographic Dark Energy
- Modified cosmology from quantum deformed entropy
- Barrow and Tsallis entropies after the DESI DR2 BAO data
- Inflation Based on the Tsallis Entropy
- Modified Friedmann equations from fractional entropy
- Investigation of generalised uncertainty principle effects on FRW cosmology
- Apparent dark matter as a non-local manifestation of emergent gravity
- Constraints on Barrow and Tsallis Holographic Dark Energy from DESI DR2 BAO data
- Rényi Holographic Dark Energy
- Barrow Holographic Dark Energy in Brane World Cosmology
- Interacting Barrow Holographic Dark Energy in Non-flat Universe
- Horizon thermodynamics and cosmological equations: A holographic-like connection between thermostatistical quantities on a cosmological horizon and in the bulk
- Holographic reconstruction of k-essence model with Tsallis and the most generalized Nojiri-Odintsov version of holographic dark energy
- Look beyond additivity and extensivity of entropy for black hole and cosmological horizons
- Barrow Cosmology and Big-Bang Nucleosynthesis
- Apparent Dark Matter Inspired by Einstein Equation of State
- Signatures of modified gravity from the gravitational Aharonov-Bohm effect
- Constraints on Rényi Entropy through Primordial Big-Bang Nucleosynthesis and Baryogenesis
- Constant-roll inflation and primordial black holes within Barrow entropic framework