Topological signatures and geometrothermodynamics of critical phenomena in regularized Maxwell black holes
Sekhmani Y. Luciano G.G. Maurya S.K. Rayimbaev J. Jasim M.K. Ibragimov I. Muminov S.
December 2025Elsevier B.V.
Physics of the Dark Universe
2025#50
We study the thermodynamic topology and microscopic interaction properties of charged black holes in RegMax gravity, focusing on the role of the coupling parameter α. Using the Duan topological current method together with Ruppeiner geometry, we show that α controls a sharp change in phase structure. Above a certain critical threshold, we find that the Duan defect curve develops an intermediate branch and vertical tangency points, producing continuous (second-order) critical behaviour. Furthermore, the Ruppeiner curvature becomes negative at very small horizon radii before turning positive and progressively vanishing at larger radii. By contrast, below the critical value of the coupling, the intermediate black hole phase disappears, and the system shows a simpler small/large first-order/coexistence behaviour driven by free-energy competition. In this regime, the Ruppeiner curvature remains predominantly positive. Overall, increasing α enriches the thermodynamic topology (allowing for second-order criticality) while simultaneously reducing the domain in which classical energy conditions (ECs) are satisfied, thus linking exotic thermodynamic behaviour to more severe violations of standard energy conditions. Copyright
Black holes , RegMax gravity , Thermodynamics
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Center for Theoretical Physics, Khazar University, 41 Mehseti Street, Baku, AZ1096, Azerbaijan
Centre for Research Impact & Outcome, Chitkara University Institute of Engineering and Technology, Chitkara University, Punjab, Rajpura, 140401, India
Institute of Nuclear Physics, Ibragimova, 1, Almaty, 050032, Kazakhstan
Department of Mathematical and Physical Sciences, College of Arts and Sciences, University of Nizwa, P.O. Box 33, Nizwa 616, Oman
Departamento de Química, Física y Ciencias Ambientales y del Suelo, Escuela Politécnica Superior – Lleida, Universidad de Lleida, Av. Jaume II, 69, Lleida, 25001, Spain
Urgench State University, Kh. Alimjan Str. 14, Urgench, 221100, Uzbekistan
University of Tashkent for Applied Sciences, Str. Gavhar 1, Tashkent, 100149, Uzbekistan
National University of Uzbekistan, Tashkent, 100174, Uzbekistan
Tashkent State Technical University, Tashkent, 100095, Uzbekistan
Kimyo International University in Tashkent, Shota Rustaveli street 156, Tashkent, 100121, Uzbekistan
Mamun University, Bolkhovuz Street 2, Khiva, 220900, Uzbekistan
Center for Theoretical Physics
Centre for Research Impact & Outcome
Institute of Nuclear Physics
Department of Mathematical and Physical Sciences
Departamento de Química
Urgench State University
University of Tashkent for Applied Sciences
National University of Uzbekistan
Tashkent State Technical University
Kimyo International University in Tashkent
Mamun University
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