arXiv subjects

Soumya Samrat Mandal

Publications and source records attributed to Soumya Samrat Mandal.

3 recordsLinked to original sources

arXiv2026

Electromagnetic Emission from a Black Hole Evaporating in External Magnetic Field

We describe a classical (non-quantum) radiation process: additional (to Hawking) emission by a black hole evaporating in an external magnetic field in vacuum. The electromagnetic radiation process is completely electric charge-free and bears some resemblance to the Gertsenshtein-Zel'dovich effect. The time evolution of the spacetime metric perturbs a static background magnetic field, inducing a radiative field that acts as an effective electromagnetic source even in the absence of physical charges or currents. To isolate the dynamic effects of the time-dependent spacetime on the external magnetic field, we approximate Hawking radiation as a spherically symmetric outflow of null fluid governed by the prescribed time-dependence of the central mass $M(t)$. We employ Laplace transform, which selects the retarded outgoing branch of the electromagnetic response, producing fields proportional to $Θ(t-r)$ and thereby fixing a causal radiative arrow of emission. The emitted spectral energy is red-dominated, scaling as $d\mathcal{E}_B/dω\propto B_0^2 m_0^2 τ_H^{-2/3} ω^{-8/3}$, where $τ_H$ is the Hawking evaporation timescale, and corresponds to a pure Transverse Electric (TE) mode. There is no final bright burst at the end of the evaporation. We offer classical analogues for this mechanism as transmission-line emission and, separately, as the displacement current emission from a medium with time-varying dielectric permittivity.

astro-ph.HE↗

arXiv2023

Constant Curvature 3-branes in 5-D f(R) Bulk

Braneworld models remain the most promising candidates to address several important questions in low-energy particle phenomenology and cosmology. The role of the moduli field(s) and its stabilization is an integral part of this question. In this work, we show that a 5-dimensional warped braneworld model with higher curvature gravity in bulk admits de-Sitter and anti de-Sitter solutions on the branes. The remarkable feature of having a positive vacuum energy on the visible brane is the presence of a metastable minimum and a global minimum for the modulus potential. While the metastable minimum leads to a consistent cosmological model of a bouncing universe, the concomitant existence of the global minimum provides a vacuum for the modulus to roll down to stability. Further, this model is shown to be consistent with the swampland conjecture to qualify as a viable candidate in the low energy description of string landscape

hep-th↗

arXiv2023

Novel modulus stabilization mechanism in higher dimensional f(R) Gravity

In this work, we obtain a new warped solution for a 5-dimensional $f(R) $ gravity in an anti de-Sitter bulk. The higher curvature term in the gravity action is shown to modify the usual warped metric. The novel feature of this modification leads to a natural geometric stabilization of the modulus/radion field in the underlying effective theory on the visible 3-brane without the need for any external stabilizing field. It is further shown that the stabilized value of the modulus resolves the well-known gauge hierarchy problem without any unnatural fine-tuning of the model parameters. This new solution also opens up the possibilities of new signatures in various scenarios formulated in the backdrop of higher dimensional space-time.

gr-qc↗