Kerr-Sen-like Lorentz violating black holes and Superradiance phenomena

TL;DR

This paper investigates how Lorentz violation in Einstein-bumblebee gravity affects Kerr-Sen-like black holes, particularly their superradiance phenomena and stability, and compares theoretical predictions with observational data from M87*.

Contribution

It introduces a Kerr-Sen-like black hole solution within Einstein-bumblebee gravity and analyzes the impact of Lorentz violation on superradiance and black hole stability.

Findings

Superradiance is enhanced for negative Lorentz-violating parameter values.

Scalar field instability regions expand with negative Lorentz violation.

Constraints on black hole parameters are derived from shadow observations.

Abstract

A Kerr-Sen-like black hole solution results from Einstein-bumblebee gravity. It contains a Lorentz violating (LV) parameter that enters when the bumblebee field receives vacuum expectation value through a spontaneously breaking of the symmetry of the classical action. The geometrical structure concerning the singularity of this spacetime is studied with reference to the parameters involved in the Kerr-Sen-like metric. We introduce this Einstein-bumblebee modified gravity to probe the role of spontaneous Lorentz violation on the superradiance scattering phenomena and the instability associated with it. We observe that for the low-frequency range of the scalar wave the superradiance scattering gets enhanced when the Lorentz-violating parameter $\ell$ takes the negative values and it reduces when values of $\ell$ are positive. The study of the black hole bomb issue reveals that for the negative values of $\ell$, the parameter space of the scalar field instability increase prominently, however, for its positive values, it shows a considerable reduction. We also tried to put constraints on the parameters contained in the Kerr-Sen-like black hole by comparing the deformation of the shadow produced by the black hole parameters with the observed deviation from circularity and the angular deviation from the $M87*$ data.