Choose timezone
Your profile timezone:
Powered by Indico
v3.3.3
General relativity as a theory of gravity is tested with flying colours in the weak field regime. However, it is unclear whether the theory is correct in the strong field regime. Black holes are the solution of Einstein field equations and are natural candidates to test the theory in the strong field regime. Black hole solutions bring major drawbacks to the GR. These have some regions where spacetime curvature blows up.Moreover, Hawking radiation from the black holes can lead to complete evaporation of the black hole and therefore violates quantum unitarity. These motivate us to test GR in the vicinity of BHs. Recent gravitational wave detections from the binary black hole merger have opened such doors. However, the ringdown portion of the signal cannot rule out possible BH alternatives (that is absence of horizon) which can cure previously stated drawbacks of black holes. It follows from BH perturbation theory that the ringdown waveform detected by LIGO can be mimicked by any compact object with a photon sphere. Either these compact objects are supported by exotic matter fields or motivated by modified theory. Collectively, they are known as exotic compact objects. At this point, it naturally comes to mind whether they are stable under linear perturbations. Otherwise, their existence is questionable. In this talk, I will consider wormholes on the brane as a possible black hole mimicker. It is well known that within the context of general relativity, they violate energy conditions.Interestingly, Kar-Lahiri-Sengupta’s work showed that wormholes on the brane do not require any exotic matter to sustain the geometry. Here we have studied the scalar, electromagnetic and axial gravitational perturbation of the wormhole. We have found that it is stable under these perturbations.Moreover, the ringdown part of the signal contains late-time echoes of the primary signal. In the next part of the talk, I will model the Damour-Solodukhin wormhole residing inside the galactic halo and show that it is a viable mimicker of a galactic black hole. Moreover, we will see that it is more stable than its isolated counterpart. Finally, we will model a star like ECO by putting a partially reflecting surface near the location of the would-be horizon. Considering plasma accretion around this ECO spacetime, we have studied the propagation of electromagnetic waves through plasma. I will discuss interesting phenomenology regarding this perturbation scheme.