Frolov–AdS black holes immersed in a string fluid: Harmonic oscillations, phase structure, and topological classification
Gashti S.N. Sekhmani Y. Afshar M.A.S. Alipour M.R. Jawad A. Sakallı İ. Pourhassan B. Shaymatov S. Sadeghi J. Rayimbaev J.
December 2025Elsevier B.V.
Physics of the Dark Universe
2025#50
This work examines the thermodynamic topology of Frolov–AdS black holes with a surrounding string fluid, highlighting the role of topological charges in determining stability. By analyzing vector fields constructed from the free energy, we identify zero points corresponding to distinct topological charges, which vary with entropy-related parameters. Our findings demonstrate that the system exhibits topological charges of +1, 0, or −1, serving as a robust criterion for black hole stability classification. Furthermore, we examine photon sphere (PS) configurations, revealing that their associated (PS = −1) reflect underlying geometric and thermodynamic structures of black hole. This study establishes connections between winding numbers and black hole phase transitions. Comparative analyses with classical black holes support the universality of the topological framework. Complementarily, the analysis of quasi-periodic oscillations elucidates the intricate interplay of electric charge, spin, cosmological constant, and string-fluid background on epicyclic and precessional motions around charged AdS black holes. Electric charge diminishes gravitational binding, shifting characteristic frequencies outward, while spin-induced frame dragging enhances orbital stability and periapsis advance. The AdS curvature associated with a negative cosmological constant universally suppresses oscillatory frequencies and modifies periastron dynamics, whereas the string-fluid parameter governs asymptotic decay rates and far-field behavior. These combined effects yield comprehensive predictions for quasinormal mode spectra and potential astrophysical signatures.
Frolov-AdS black holes , Harmonic oscillations , Thermodynamic topology
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Department of Physics, Faculty of Basic Sciences, University of Mazandaran, P.O. Box 47416-95447, Babolsar, Iran
School of Physics, Damghan University, Damghan, P. O. Box 3671641167, Iran
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
Institute of Fundamental and Applied Research, National Research University TIIAME, Kori Niyoziy 39, Tashkent, 100000, Uzbekistan
University of Tashkent for Applied Sciences, Gavhar Str. 1, Tashkent, 100149, Uzbekistan
Physics Department, Eastern Mediterranean University, North Cyprus via Mersin 10, Famagusta, 99628, Turkey
Department of Mathematics, COMSATS University, Islamabad, Lahore-Campus, Lahore, 54000, Pakistan
Institute for Theoretical Physics and Cosmology, Zhejiang University of Technology, Hangzhou, 310023, China
Western Caspian University, Baku, AZ1001, Azerbaijan
Tashkent State Technical University, Tashkent, 100095, Uzbekistan
Urgench State University, Kh. Alimjan Str. 14, Urgench, 221100, Uzbekistan
National University of Uzbekistan, Tashkent, 100174, Uzbekistan
Canadian Quantum Research Center, Ave Vernon, BC V1T 2L7, 204-3002 32, Canada
Department of Physics
School of Physics
Center for Theoretical Physics
Centre for Research Impact & Outcome
Institute of Nuclear Physics
Department of Mathematical and Physical Sciences
Institute of Fundamental and Applied Research
University of Tashkent for Applied Sciences
Physics Department
Department of Mathematics
Institute for Theoretical Physics and Cosmology
Western Caspian University
Tashkent State Technical University
Urgench State University
National University of Uzbekistan
Canadian Quantum Research Center
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