Study of a global monopole surrounded by perfect fluid in a static dyonic black hole

Abstract

We study a static dyonic black hole endowed with a global monopole and surrounded by a perfect fluid with an equation-of-state parameter ω . This parameter relates to distributions of radiation, dust, and dark matter. We use a modified lapse function to examine the horizon structure, thermodynamic properties, and phase transitions. The heat capacity shows critical behavior that divides stable and unstable phases. Curvature invariants confirm that the central singularity persists. Next, we calculate the photon sphere and shadow radius. We constrain the model parameters using observations from Sgr A*, which indicates that both the global monopole and surrounding matter significantly affect the shadow size. We analyze dynamical properties with the effective potential and quasi–normal modes using the WKB method. This shows that oscillation frequencies and damping rates are very sensitive to the matter distribution, and all modes indicate linear stability. Moreover, we investigate the greybody bound, emitted power spectrum, and partial absorption cross–section. These findings reveal that environmental effects change the potential barrier and the observable Hawking radiation spectrum. Finally, we conduct a topological analysis of the photon sphere and thermodynamic potentials to clarify the system’s stability properties. These results highlight how environmental matter and topological defects shape black hole physics. © 2026 The Authors.