arXiv subjects

Suvikranth Gera

Publications and source records attributed to Suvikranth Gera.

7 recordsLinked to original sources

arXiv2025

Impact of neglecting center-of-mass acceleration in parameter estimation of stellar-mass black holes

A tertiary body near a coalescing binary can imprint its influence on the gravitational waves (GWs) emitted by that binary in the form of center-of-mass (CoM) acceleration. An example of such a scenario is a binary black hole (BBH) merging near a supermassive black hole, which is touted to occur frequently. The limited low-frequency sensitivity of current GW detectors makes it challenging to detect these effects, as the associated waveform phase remains elusive. However, next-generation (3G) detectors such as Cosmic Explorer (CE) and Einstein Telescope (ET), with improved sensitivity at lower frequencies, are expected to be capable of capturing such signatures. In our study, we focus on the stellar-mass BBHs and explore the parameter space where the CoM acceleration will play a dominant role affecting parameter inference of the binary. We demonstrate that an unaccounted CoM acceleration of a low-mass binary with a total mass of $5\, \rm{M}_{\odot} $ can lead to significant systematic biases, exceeding statistical errors in the estimation of the chirp mass and symmetric mass ratio when the CoM parameter $\alpha$ is as small as $\sim 10^{-9}$ and $10^{-10}$ $\rm{s}^{-1}$ for CE and ET, respectively. We also find that asymmetric binaries are more susceptible to systematic bias when CoM acceleration is neglected. When the effect of CoM acceleration is included in the GW phase, then $\alpha = 10^{-7} \rm s^{-1}$ can be constrained with a bound of $10^{-9} (10^{-11})\, \rm s^{-1}$ for CE (ET). Our study thus highlights the crucial implications of considering the presence of a tertiary body in the GW emitted by a stellar-mass BBH when observed in 3G detectors.

gr-qc↗

arXiv2024

Shadows of generalised Hayward spacetimes : in vacuum and with plasma

We investigate the shadow properties of a wide class of spacetimes arising from different parameter regimes of the generalized Hayward metric, characterized by two independent parameters $(\sigma, \kappa)$ (Phys. Rev. D 106, 044028). This metric extends the original Hayward regular black hole solution by introducing distinct mass functions in the $g_{tt}$ and $g_{rr}$ components, giving rise to four types of wormholes ( which include multi-peak effective potentials), a regular black hole, and a singular black hole solutions allowing for a unified treatment of black hole mimickers. We compute the shadow radii for all spacetimes in vacuum and in the presence of plasma, using both homogeneous and non-homogeneous plasma profiles. Our results show that certain wormhole solutions particularly the Hayward-Damour-Solodukhin class can exhibit multiple photon spheres, leading to shadow features that differ significantly from the Schwarzschild black hole. When these results are compared with Event Horizon Telescope observations of Sgr~$A^\star$, we find that regular black holes remain observationally viable but only within a narrow parameter space. In contrast, wormhole solutions with multi-peak effective potentials are more consistent with shadow constraints than those with single peaks. This contrasts with quasinormal mode studies, which favored single-barrier potentials, and may imply detectable late-time echoes in gravitational wave signals.

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arXiv2023

Black holes in degenerate Einstein Gauss-Bonnet gravity: Can QNMs distinguish them from GR?

In this study, for the first time, we analyse the quasinormal modes of black holes occurring within the framework of degenerate gravity. We investigate the properties of the asymptotically flat spacetimes introduced recently in [JCAP 02(2022)02] that satisfy degenerate Einstein Gauss-Bonnet(dEGB) action and belong to a much larger class of solutions which include cosmological constant. This solution has two distinct branches akin to Einstein Gauss-Bonnet(EBG) gravity. However, unlike the EBG solutions, both the branches of dEGB are well-defined asymptotically. The negative branches from both theories can be identified for the asymptotically flat case. We observe black holes for specific ranges of the Gauss-Bonnet coupling parameter and perform a stability analysis by calculating the quasinormal modes (QNMs) under scalar wave propagation. Finally, the ringdown spectrums of our black holes are compared with their GR counterparts.

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arXiv2021

Two-dimensional gravity from vanishing metrical dimensions

We obtain a dynamical formulation of two-dimensional gravity from a non-Einsteinian phase in higher dimensions $(D=3+2n)$. The formalism is associated with (at least) one extra dimension of vanishing proper length, thus being inequivalent to either a Kaluza-Klein compactification or the Mann-Ross dimensional reduction defined upon a singular limit. The emergent solutions admit any arbitrary curvature in contrast with Jackiw-Teitelboim constant curvature gravity. We present the static and homogeneous solutions as explicit examples. The effective field equations are shown to remain unaffected by the inclusion of higher Lovelock terms beyond Einstein.

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arXiv2021

Finite model of an electric charge

We set up a model of an electric charge where the noninvertible metric phase of first order gravity supercedes the point charge singularity in a curved spacetime. A topological interpretation of the electric charge is provided in terms of an index defined for the degenerate spacetime solution, being closely related to the Euler characteristic. The gravitational equations of motion at this phase are found to be equivalent to the laws of electrostatics. The associated field energy is finite and the geometry sourcing the charge is regular.

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arXiv2020

Magnetic monopole as a spacetime defect

We propose that the only possible realization of a magnetic pole is emergent, it being an artefact of a torsion defect in a curved spacetime. This special phase is characterized by a class of degenerate metric spacetime solutions of first order gravity in vacuum. The (apparent) magnetic charge is shown to have a topological origin, given by a lower dimensional counterpart of the Nieh-Yan index. At the invertible metric phase at a distance, this topological charge gets reflected as the (magnetic) Reissner-Nordstrom charge to an asymptotic observer, even though the defect itself remains hidden.

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arXiv2019

Taming Dirac strings and timelike loops in vacuum gravity

The problem of singularities associated with Dirac strings and closed timelike curves in classical solutions of pure gravity is analyzed here. A method to eliminate these is introduced and established first for the Taub-NUT geometry. This is superceded by a smooth solution of first order field equations, which is defined to be a unique extension of the Taub Universe to a degenerate metric phase. As an additional feature, this framework naturally provides a geometric interpretation of the magnetic charge in the context of gravity theory without matter. Finally, exploiting the two phases of the metric determinant, we find a (smooth and unique) continuation of the Misner geometry as well, ridding it of closed timelike worldlines which exist in its otherwise Einsteinian manifestation.

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