Long-lived quasinormal frequencies for regular black hole supported by the Einasto profile in the presence of the magnetic field

TL;DR

This study analyzes quasinormal modes, grey-body factors, and absorption cross-sections of a scalar field in regular black holes supported by the Einasto profile, revealing how environmental and magnetic parameters influence long-lived modes and scattering properties.

Contribution

It introduces a detailed analysis of how the Einasto profile and magnetic field affect black hole quasinormal modes and related scattering phenomena, highlighting the role of effective mass and environmental parameters.

Findings

Increasing effective mass suppresses damping, leading to long-lived modes.

Grey-body factors from different methods agree well, with controlled differences.

Transition from low-frequency suppression to high-frequency absorption is demonstrated.

Abstract

We investigate quasinormal modes, grey-body factors, and absorption cross-sections of a massive scalar field in regular black-hole spacetimes supported by the Einasto density profile. The analysis is performed for $\tilde n=1/2$, $1$, and $5$, where the scalar mass $\mu$ is treated as an effective parameter induced by an external environment. Quasinormal frequencies are computed with high-order WKB expansions and Pad\'e resummation, and are cross-checked by time-domain evolution. We show that increasing the effective mass and varying the Einasto parameters can strongly suppress the damping rate, leading to long-lived modes and clear quasi-resonant behavior. Grey-body factors obtained from direct WKB transmission and from the QNM-based correspondence agree well in the considered regimes, while their differences remain controlled. Using the transmission coefficients, we derive partial and total absorption cross-sections and demonstrate the expected transition from low-frequency suppression to efficient high-frequency absorption. Our results show that regularity of the core together with environmental parameters leaves a noticeable imprint on both ringdown and scattering observables. Within this setup, the magnetic field acts as the physical agent that controls the effective mass scale and therefore governs how close the system can approach the quasi-resonant regime.