https://doi.org/10.1140/epjp/s13360-026-07849-5
Regular Article
Photon sphere, particle dynamics and QPOs in charged AdS black hole with a cloud of strings surrounded by quintessence within Rastall gravity
Department of Physics, The Assam Royal Global University, 781035, Guwahati, Assam, India
a
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Received:
20
January
2026
Accepted:
19
May
2026
Published online:
1
June
2026
Abstract
In this work, we performed a comprehensive theoretical investigation of the optical and dynamical properties of static, charged anti-de Sitter (AdS) black holes surrounded by a cloud of strings and a quintessence-like fluid, within the framework of Rastall gravity. We derive the effective potential for null geodesics and analyze key features, such as the effective force, photon trajectories, and circular null orbits (photon sphere). Furthermore, we studied the dynamics of neutral test particles using the Hamilton–Jacobi formalism, with particular focus on the innermost stable circular orbit. Using the effective potential governing massive particle motion, we investigated quasi-periodic oscillations (QPOs) and computed the fundamental oscillation frequencies. Our results demonstrate how the presence of a string cloud, quintessence-like fluid, and deviations from general relativity significantly affect both the optical and dynamical properties of the BH space–time.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2026
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
