https://doi.org/10.1140/epjp/s13360-026-07660-2
Regular Article
Effects of matter with anisotropic pressure on the Fan–Wang regular black hole shadows
1
National Nanotechnology Laboratory of Open Type, 050040, Almaty, Kazakhstan
2
Al-Farabi Kazakh National University, Al-Farabi Av. 71, 050040, Almaty, Kazakhstan
3
Divisione di Fisica, Università di Camerino, Via Madonna delle carceri 9, 62032, Camerino, Italy
4
Department of Nanoscale Science and Engineering, University at Albany-SUNY, 12222, Albany, New York, USA
5
INAF - Osservatorio Astronomico di Brera, Milan, Italy
6
Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Perugia, 06123, Perugia, Italy
7
ICRANet, Piazza della Repubblica 10, 65122, Pescara, Italy
a
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Received:
26
October
2025
Accepted:
6
April
2026
Published online:
18
April
2026
Abstract
In this work, we investigate the consequences of an exotic fluid exhibiting negative radial and tangential pressures—thereby violating the Zel’dovich limit—on a regular solution that generalizes the Schwarzschild black hole. Specifically, we focus on the regular Fan–Wang spacetime and analyze how the presence of such a fluid modifies the black hole shadow images through negative equations of state for both pressure components. Although fundamentally different from quintessence, we consider constant radial and tangential state parameters to emulate, but not reproduce, the effects of dark energy. Furthermore, we explore the main properties of infalling spherical accretion flows and study how these state parameters influence the horizons, photosphere, and impact parameter of the Fan–Wang black hole. We determine the black hole shadow by analyzing the null geodesics of massless test particles in the background spacetime, which serves as a reference geometry. The physical photon shadow is obtained using the effective metric induced by nonlinear electrodynamics. We examine the observed intensity under two spherical accretion scenarios in both geometries. Finally, we provide a physical interpretation of the role of negative pressures in our results and discuss possible extensions of this framework to the isotropic case.
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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.
