Non-extensive Entropy and Holographic Thermodynamics: Topological Insights
Saeed Noori Gashti, B. Pourhassan
TL;DR
The paper studies holographic thermodynamics of AdS Einstein–Gauss–Bonnet black holes using non-extensive entropies (Barrow, Rényi, Sharma–Mittal) in both bulk-boundary and restricted phase space (RPS) frameworks. It shows that in bulk-boundary thermodynamics the topological charges, determined by Duan’s φ-mapping and winding numbers, vary with the non-extensive parameters (δ, λ, α, β): Barrow yields three or two charges depending on δ, Rényi can increase the number of charges as λ→0, and Sharma–Mittal’s charge count depends on the proximity of α and β. In stark contrast, the RPS framework exhibits a remarkable consistency, with a fixed topological charge ω = +1 and total charge W = +1 across all entropies and parameter choices, even reducing to the Bekenstein–Hawking case. This dichotomy highlights the robustness of RPS in capturing stable thermodynamic topology and suggests that non-extensive entropy effects are framework-dependent for black hole thermodynamics. The work advances understanding of how holographic black hole thermodynamics responds to generalized entropy forms and offers a pathway to more reliable topological classifications in gravitational systems.
Abstract
In this paper, we delve into the thermodynamic topology of AdS Einstein-Gauss-Bonnet black holes, employing non-extensive entropy formulations such as Barrow, Rényi, and Sharma-Mittal entropy within two distinct frameworks: bulk boundary and restricted phase space (RPS) thermodynamics. Our findings reveal that in the bulk boundary framework, the topological charges, are influenced by the free parameters and the Barrow non-extensive parameter $(δ)$. So, we faced three topological charges $(ω= +1, -1, +1)$. When the parameter $δ$ increases to 0.9, the classification changes, resulting in two topological charges $(ω= +1, -1)$. When $δ$ is set to zero, the equations reduce to the Bekenstein-Hawking entropy structure, yielding consistent results with three topological charges. Additionally, setting the non-extensive parameter $λ$ in Rényi entropy to zero increases the number of topological charges, but the total topological charge remains (W = +1). The presence of the Rényi non-extensive parameter alters the topological behavior compared to the Bekenstein-Hawking entropy. Sharma-Mittal entropy shows different classifications and the various numbers of topological charges influenced by the non-extensive parameters $α$ and $β$. When $α$ and $β$ have values close to each other, three topological charges with a total topological charge $(W = +1)$ are observed. Varying one parameter while keeping the other constant significantly changes the topological classification and number of topological charges. In contrast, the RPS framework demonstrates remarkable consistency in topological behavior. Under all conditions and for all free parameters, the topological charge remains $(ω= +1)$ with the total topological charge $(W = +1)$. This uniformity persists even when reduced to Bekenstein-Hawking entropy.