Quasinormal modes of a black hole surrounded by a fluid of strings in Rastall gravity*

Abstract In this paper, we explore the quasinormal modes (QNMs) of a black hole surrounded by a fluid of strings within the framework of Rastall gravity. We analyze the behavior of scalar, electromagnetic, and gravitational perturbations, focusing on the influences of black hole charge Q and angular momentum l on the quasinormal frequencies. Our numerical results reveal a significant dependence on parameter ε . These trends are consistent across different types of perturbations, emphasizing the relationship between black hole parameters and QNM behavior.