Metric-affine gravity modifications to black hole Hawking radiations and stability analysis

In this study, we explore black hole solutions in the framework of Metric-Affine Gravity, a generalized theory that treats the spacetime metric and affine connection as independent variables and incorporates torsion and nonmetricity. We begin by considering static, spherically symmetric black hole solutions in MAG, where the lapse function is modified due to contributions from spin, dilation, and shear charges. This leads to a generalized Reissner–Nordström-like geometry, but without invoking any electromagnetic field. We then analyze the Hawking evaporation process by computing the photon sphere radius and the critical impact parameter. Our results show that the Lagrangian parameters [Formula: see text], [Formula: see text], and the AdS radius [Formula: see text] strongly influence the rate of Hawking radiation and the black hole’s lifetime. Notably, larger values of [Formula: see text] and [Formula: see text] lead to slower evaporation, suggesting that MAG corrections can stabilize black holes against rapid decay. To assess the dynamical response of these modified black holes, we study the evolution of massless scalar perturbations. By converting the perturbation equation into a Schrödinger-like form, we analyze the effective potential and simulate the time evolution using a finite difference method. Our findings indicate that the damping rates and oscillation frequencies of scalar perturbations are significantly affected by the geometric charges and Lagrangian parameters. Finally, we compute bounds on the greybody factors, which represent the probability that Hawking radiation can escape the black hole’s potential barrier. Using the Boonserm–Visser technique, we show that the spin charge enhances the transmission probability, while higher dilation and shear charges reduce it. These results highlight how torsion and nonmetricity not only alter the spacetime structure but also regulate the thermal and quantum emission processes near the black hole horizon.