Confining nonlinear electrodynamics black holes: from thermodynamic phases to high-frequency phenomena with accretion process

TL;DR

This paper explores a novel confining nonlinear electrodynamics black hole model, analyzing its thermodynamic properties, gravitational lensing, shadow, and accretion phenomena, demonstrating potential to explain high-frequency oscillations in black hole systems.

Contribution

It introduces a new black hole solution with confining nonlinear electrodynamics, analyzing its thermodynamics, lensing, shadow, and accretion, linking theoretical predictions with observable phenomena.

Findings

Reduced gravitational lensing compared to Schwarzschild

Phase transitions in thermodynamic properties

Enhanced accretion rates and quasi-periodic oscillations

Abstract

We investigate a static, spherically symmetric black hole solution arising from Einstein gravity coupled to a confining nonlinear electrodynamics model that reproduces Maxwell theory in the strong-field regime while introducing confinement-like corrections at large distances. The resulting metric function is asymptotically Schwarzschild but carries a characteristic Q^3/(9\xi^2 r^4) correction, where $Q$ is the magnetic charge and $\xi$ is the nonlinear electrodynamics parameter, with the conventional Reissner-Nordstr\"om term Q^2/r^2 absent. We analyze the horizon structure and construct three-dimensional embedding diagrams to visualize spatial geometry. Using the Gauss-Bonnet theorem, we compute the weak-field deflection angle in vacuum, cold plasma, and axion-plasmon media, finding that the nonlinear electromagnetic corrections reduce the total bending compared to Schwarzschild at fixed Arnowitt-Deser-Misner mass. The gravitational redshift, Joule-Thomson expansion coefficient, and heat capacity are derived, revealing phase transitions and inversion curves that depend on the model parameters. We obtain closed-form expressions for the photon sphere radius, Lyapunov exponent, and shadow size, demonstrating their sensitivity to Q and $\xi$ along observable Intensities. Fully relativistic hydrodynamical simulations of Bondi-Hoyle-Lyttleton accretion show that the confining geometry produces a $\sim 40\%$ enhancement in mass accretion rate relative to Schwarzschild and generates quasi-periodic oscillations with stable 3:2 and 2:1 frequency ratios matching observations from black hole X-ray binaries. These results establish the confining nonlinear electrodynamics black hole as a testable model that can reproduce high-frequency quasi-periodic oscillation pairs without invoking black hole spin.