My research encompasses various aspects of black hole physics. I am particularly interested in the internal structure of black holes and questions related to the stability of the quasinormal mode spectrum of black holes.
Please visit my INSPIRE-HEP profile for bibliometrics and a possibly updated list of papers.
@article{Sarkar:2023rhp,abbr={PRD},bibtex_show={true},author={Sarkar, Subhodeep and Rahman, Mostafizur and Chakraborty, Sumanta},title={{<a href="https://doi.org/10.1103/PhysRevD.108.104002">Perturbing the perturbed: Stability of quasinormal modes in presence of a positive cosmological constant</a>}},eprint={2304.06829},archiveprefix={arXiv},primaryclass={gr-qc},doi={10.1103/PhysRevD.108.104002},journal={Phys. Rev. D},volume={108},number={10},pages={104002},year={2023}}
We attempt to address the question of whether standard tests of general relativity can detect the presence of a black hole carrying a supertranslation field. In this regard, we study the photon sphere of a dynamical black hole carrying a supertranslation hair. We find that the dynamics of the photon sphere is quite subtle and it may offer an opportunity to differentiate a supertranslated black hole from its bald counterpart. This represents a first step toward understanding the observational signatures of a supertranslated dynamical black hole.
@article{Sarkar:2021djs,abbr={PRD},bibtex_show={true},author={Sarkar, Subhodeep and Kumar, Shailesh and Bhattacharjee, Srijit},title={<a href="https://doi.org/10.1103/PhysRevD.105.084001">Can we detect a supertranslated black hole?</a>},arxiv={2110.03547},eprint={<a href="https://doi.org/10.48550/arXiv.2110.03547">2110.03547</a>},archiveprefix={arXiv},primaryclass={gr-qc},doi={10.1103/PhysRevD.105.084001},journal={Phys. Rev. D},volume={105},number={8},pages={084001},year={2022},inspire={https://inspirehep.net/literature/1940051},selected={false}}
We study linear scalar perturbations of black holes in two-dimensional (2D) gravity models with a particular emphasis on Jackiw-Teitelboim (JT) gravity. We obtain an exact expression of the quasinormal mode frequencies for single horizon black holes in JT gravity and then verify it numerically using the Horowitz-Hubeny method. For a 2D Reissner-Nordström like solution, we find that the massless scalar wave equation reduces to the confluent Heun equation using which we calculate the Hawking spectra. Finally, we consider the dimensionally reduced Bañados-Teitelboim-Zanelli (BTZ) black hole and obtain the exterior and interior quasinormal modes. The dynamics of a scalar field near the Cauchy horizon mimics the behavior of the same for the usual BTZ black hole, indicating a possible violation of the strong cosmic censorship conjecture in the near extreme limit. However, quantum effects seem to rescue strong cosmic censorship.
@article{Bhattacharjee:2020nul,abbr={PRD},bibtex_show={true},author={Bhattacharjee, Srijit and Sarkar, Subhodeep and Bhattacharyya, Arpan},title={<a href="https://doi.org/10.1103/PhysRevD.103.024008">Scalar perturbations of black holes in Jackiw-Teitelboim gravity</a>},eprint={<a href="https://doi.org/10.48550/arXiv.2011.08179">2011.08179</a>},author+an={2=highlight},arxiv={2011.08179},archiveprefix={arXiv},primaryclass={gr-qc},doi={10.1103/PhysRevD.103.024008},journal={Phys. Rev. D},volume={103},number={2},pages={024008},year={2021},inspire={https://inspirehep.net/literature/1830603},selected={false}}
We study the phenomena of mass inflation using the Ori model for a rotating Bañados-Teitelboim-Zanelli (BTZ) black hole that is sufficiently far from extremality, and show that the right Cauchy horizon (\(CH^+_R\)) of the BTZ black hole becomes singular. Motivated by the recent analysis of Dias, Reall, Santos [J. High Energy Phys. 12 (2019) 097], we choose the retrograde quasinormal modes to govern the decay of perturbations exterior to the black hole. The resulting model captures the violation of the strong cosmic censorship conjecture near extremality. On the other hand, far from extremality, the
\(CH^+_R\)of a BTZ black hole develops a weak null singularity. Our analysis shows a slowly rotating BTZ black hole will respect strong cosmic censorship.
@article{Bhattacharjee:2020gbo,abbr={PRD},bibtex_show={true},author={Bhattacharjee, Srijit and Kumar, Shailesh and Sarkar, Subhodeep},title={<a href="https://doi.org/10.1103/PhysRevD.102.044030">Mass inflation and strong cosmic censorship in a nonextreme BTZ black hole</a>},eprint={<a href="https://doi.org/10.48550/arXiv.2005.09705">2005.09705</a>},arxiv={2005.09705},archiveprefix={arXiv},primaryclass={gr-qc},doi={10.1103/PhysRevD.102.044030},journal={Phys. Rev. D},volume={102},number={4},pages={044030},year={2020},inspire={https://inspirehep.net/literature/1797104},selected={false}}
