Abhisek Barman Maji | Searcharxiv

arXiv2026

Signatures of charged rotating regular black holes: quasinormal modes, grey-body factors and shadows

We construct and study possible astrophysical signatures of the rotating counterparts of two charged regular black holes, namely the Ayón--Beato--García (ABG) and Balart--Panotopoulos--Rincón (BPR) spacetimes -- obtained using the Newman-Janis algorithm. After verifying the regularity of the rotating metrics, we study massless scalar perturbations, compute the quasinormal mode (QNM) spectra, and characterise their dependence on the spin and charge parameters. Grey-body factors (GBFs) are computed, and the QNM-GBF correspondence is verified. The low-frequency superradiant amplification factor is also examined via matched asymptotic expansions. The Lyapunov exponents are used to connect the eikonal QNM damping rate to photon-orbit instability. Additionally, from shadow profiles, we constrain the parameter space of rotating regular black holes using the Event Horizon Telescope (EHT) observations. Across all the probes, we find that the rotating BPR and Kerr--Newman black holes behave almost indistinguishably from one another, while the rotating ABG geometry exhibits distinct perturbative, scattering, and geometric properties, particularly at larger values of spin and charge. Our analysis indicates that differentiating between charged rotating regular black hole models may be possible using gravitational wave and shadow observations.

gr-qc↗

arXiv2026

Quasinormal spectra of a wormhole family: overtone features and a parameter-controlled redshift

Though investigated extensively in the past, we take a detailed relook at the study of quasinormal modes (QNM) in a known family of wormholes (ultrastatic ($g_{00}=-1$), as well as spacetimes with different, non-constant $g_{00}$), which includes the familiar Bronnikov-Ellis spacetime as a special case. Our focus here is to go beyond the fundamental mode and obtain some of the QNM overtones using a suitable numerical scheme. Scalar and axial gravitational QNMs including two or three overtones are obtained for the family of ultrastatic geometries and their parameter dependencies are shown explicitly. Further, we comment on how (a) the overtones may influence the time-domain profile in a perturbation and (b) in what sense, the use of overtones may help in distinguishing between different geometries within the family. Finally, we show how an effect somewhat similar to the so-called `environment induced redshift' of QNMs, introduced recently (Phys. Rev. D \textbf{111}, 064026 (2025)), may be obtained for spacetimes with non-constant $g_{00}$, via an appropriate tuning of available metric parameters which systematically modify the shapes of the effective potentials arising in the perturbation equations.

gr-qc↗