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Quasinormal modes and Grey body factors of Wormholes: From General prescription to Einstein Gauss Bonnet realizations

Madhukrishna Chakraborty, Subenoy Chakraborty

TL;DR

This work develops a comprehensive framework to distinguish traversable wormholes from black holes by analyzing quasinormal modes and greybody factors within regularized 4D Einstein–Gauss–Bonnet gravity. It provides a general prescription linking wormhole shadows, QNMs, and GBFs, and derives explicit eikonal relations that connect the shadow radius to QNM frequencies. The study compares isotropic and anisotropic EGB wormholes, giving analytic QNM and GBF expressions and showing linear stability of the fundamental scalar mode (Im(ω0)=0) across the explored parameter space. A semi-analytic justification of the QNM–shadow correspondence is presented, highlighting the role of the photon sphere and throat geometry. The results offer observationally relevant signatures for future GW detectors and shadow imaging, while acknowledging the need for a full tensor perturbation stability analysis and extensions to rotating configurations.

Abstract

Traversable wormholes are one of the most exciting predictions of General Relativity that offer short-cuts through space-time. However, their feasibility requires the violation of the null energy condition and makes their detection a bit difficult. This paper aims to show the new avenues delving deep into the observational prospects of TWHs via quasinormal modes (QNMs) and gray body factors GBFs. These are the two elementary aspects of wave dynamics. Given their distinct spectral imprints, these features provide a potential means to distinguish wormholes from black holes in gravitational wave observations. The role of QNMs in characterizing the ringdown phase of perturbations and the GBFs in determining transmission probabilities through wormhole barriers have been explored by a general description and then fed to Einstein Gauss Bonnet WH solutions in isotropic as well as anisotropic cases. Finally, a correspondence of the QNM frequencies with radius of the WH shadows has been made and the effect of Gauss Bonnet parameter on the QNM spectra has been discussed.

Quasinormal modes and Grey body factors of Wormholes: From General prescription to Einstein Gauss Bonnet realizations

TL;DR

This work develops a comprehensive framework to distinguish traversable wormholes from black holes by analyzing quasinormal modes and greybody factors within regularized 4D Einstein–Gauss–Bonnet gravity. It provides a general prescription linking wormhole shadows, QNMs, and GBFs, and derives explicit eikonal relations that connect the shadow radius to QNM frequencies. The study compares isotropic and anisotropic EGB wormholes, giving analytic QNM and GBF expressions and showing linear stability of the fundamental scalar mode (Im(ω0)=0) across the explored parameter space. A semi-analytic justification of the QNM–shadow correspondence is presented, highlighting the role of the photon sphere and throat geometry. The results offer observationally relevant signatures for future GW detectors and shadow imaging, while acknowledging the need for a full tensor perturbation stability analysis and extensions to rotating configurations.

Abstract

Traversable wormholes are one of the most exciting predictions of General Relativity that offer short-cuts through space-time. However, their feasibility requires the violation of the null energy condition and makes their detection a bit difficult. This paper aims to show the new avenues delving deep into the observational prospects of TWHs via quasinormal modes (QNMs) and gray body factors GBFs. These are the two elementary aspects of wave dynamics. Given their distinct spectral imprints, these features provide a potential means to distinguish wormholes from black holes in gravitational wave observations. The role of QNMs in characterizing the ringdown phase of perturbations and the GBFs in determining transmission probabilities through wormhole barriers have been explored by a general description and then fed to Einstein Gauss Bonnet WH solutions in isotropic as well as anisotropic cases. Finally, a correspondence of the QNM frequencies with radius of the WH shadows has been made and the effect of Gauss Bonnet parameter on the QNM spectra has been discussed.

Paper Structure

This paper contains 13 sections, 73 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Shadows, QNMs and GBFs of TWHs: a general prescription
  3. TWHs and their shadows
  4. QNMs and GBFs of TWHs
  5. TWHs in EGB Theory: QNMs and GBFs
  6. TWHs in EGB theory
  7. QNM and Grey body spectra for isotropic and anisotropic EGB WHs
  8. Some important remarks
  9. NEC Violation and Its Impact on Spectra:
  10. Nature of Perturbations and QNM Spectra:
  11. Greybody Factor Calculation and Sensitivity:
  12. Justification of the QNM–shadow correspondence: A semi-analytic approach
  13. Conclusion

Figures (5)

  • Figure 1: Variation of potential with tortoise coordinate for massless scalar field (left) and electromagnetic field (right) in case of anisotropic WH solution
  • Figure 2: Variation of potential with tortoise coordinate for massless scalar field (left) and electromagnetic field (right) for isotropic WH solution ($\rho_{0},~\Lambda=0.1$ chosen)
  • Figure 3: Variation of QNM spectra (arbitrary mode) with Gauss Bonnet parameter ($\alpha$) for anisotropic (left) and isotropic (right with ($\rho_{0},~\Lambda=0.1$ chosen)) WH solutions
  • Figure 4: Variation of fundamental mode of QNM spectra with Gauss Bonnet parameter ($\alpha$) for anisotropic (left) and isotropic (right with ($\rho_{0},~\Lambda=0.1$ chosen)) WH solutions
  • Figure 5: Variation of Im($\omega$) with the gauss bonnet parameter $\alpha$ for the anisotropic EGB WH solution and $Im(\omega_{0})=0$