arXiv subjects

Pritam Nanda

Publications and source records attributed to Pritam Nanda.

7 recordsLinked to original sources

arXiv2026

Selective enhancement of quantum decay channels

In the decay of quantum particles under field theoretic consideration, the decay rate is typically a convolution of the density of modes the primary field is allowed to decay into and the allowed probability density for the field to decay into such modes. In free space, though many such processes show high amplitude of such transitions towards the infrared sector, the depletion of allowed mode density in that regime arrests the efficacy of such decays at low energies. Therefore in free space, in order to enhance the decay rate, one needs the transition probability density to be rich enough towards the high energy sector where mode density support is also high enough to make the rate sufficiently large. In this work we argue that in the controlled boundary condition environment e.g. in a cavity, the mode functions of product field receive significant support towards their infrared sector, boosting the probability (and hence rates) of low energy processes. The cavity geometry offers sweet spots in terms of resonant geometry around which the interaction of a primary field with product fields receives dramatic enhancement, significantly enlarging its decay rates. Therefore, a judicious selection of cavity geometry serves as a potential substitute to studying interesting processes at high energy. The results have direct relevance for the study of QED processes and implications for the study of exotic new physics are also discussed.

gr-qc↗

arXiv2026

Microstate Counting for rotating (type~II) isolated horizons

We present a proposal for black hole microstate counting in Loop Quantum Gravity (LQG) for rotating (type~II) isolated horizons. The key obstacle in extending the standard nonrotating entropy derivation arises from the $\theta$-dependent rotation 1-form, which breaks the global Chern--Simons (CS) structure on the horizon. We propose a local decomposition of the horizon $S^2$ into narrow concentric rings, each approximated as a locally nonrotating patch with a constant effective CS level. Each ring is quantized independently using standard LQG techniques, and the total entropy is obtained by integrating over the entire horizon. This method restores a local CS description, includes the contribution of angular momentum, and is consistent with the first law of black hole mechanics.

gr-qc↗

arXiv2023

Hawking temperature of black holes with multiple horizons

There are several well-established methods for computing thermodynamics in single-horizon spacetimes. However, understanding thermodynamics becomes particularly important when dealing with spacetimes with multiple horizons. Multiple horizons raise questions about the existence of a global temperature for such spacetimes. Recent studies highlight the significant role played by the contribution of all the horizons in determining Hawking temperature. Here we explore the Hawking temperature of a rotating and charged black hole in four spacetime dimensions and a rotating BTZ black hole. We also find that each horizon of those black holes contributes to the Hawking temperature. The effective Hawking temperature for a four-dimensional rotating and charged black hole depends only on its mass. This temperature is the same as the Hawking temperature of a Schwarzschild black hole. In contrast, the effective Hawking temperature depends on the black hole mass and angular momentum for a rotating BTZ hole.

gr-qc↗

arXiv2023

Local first law of black hole

We investigated the form and implications of the local first law of black hole thermodynamics in relation to an observer located at a finite distance from the black hole horizon. Our study is based on the quasilocal form of the first law for black hole thermodynamics, given by $\delta E=\frac{\bar{\kappa}}{8\pi}\delta A$, where $\delta E$ and $\delta A$ represent the changes in the black hole mass and area, respectively, and $\bar{\kappa}$ denotes the quasilocal surface gravity. We show that even at a finite distance, the quasilocal law still holds. It shows how the first law scales with the observer's location.

gr-qc↗

arXiv2022

Hawking radiation in multi-horizon spacetimes using Hamilton Jacobi method

It has been recently shown that the contribution between the horizons determines the Hawking temperature for a multi-horizon spacetime. In this article, we apply the Hamiltonian Jacobi method to compute the Hawking temperature for some multi-horizon spacetimes like Schwarzschild-de Sitter spacetime (SdS), Reissner-Nordstrom-de Sitter spacetime (RNdS), and rotating BTZ black hole spacetime (RBTZ) and also arrive at the same conclusion. There are two contributions to the tunneling process of radiation. The combination of these two contributions gives the radiation with the Hawking temperature with an effective surface gravity.

gr-qc↗

arXiv2022

Hawking radiation as quantum mechanical reflection

In this article, we explore an alternative derivation of Hawking radiation. Instead of the field-theoretic derivation, we have suggested a simpler calculation based on quantum mechanical reflection from a one-dimensional potential. The reflection coefficient shows an exponential fall in energy which, in comparison with the Boltzmann probability distribution, yields a temperature. The temperature is the same as Hawking temperature for spherically symmetric black holes. The derivation gives an exact local calculation of Hawking temperature that involves a region lying entirely outside the horizon. This is a crucial difference from the tunneling calculation, where it is necessary to involve a region inside the horizon.

gr-qc↗

arXiv2020

On Super-Translation transition between Quasi-local Black holes

We re-explore the symmetries of a weakly isolated horizon (WIH) from the perspective of freedom in the choice of intrinsic data. The supertranslations are realized as additional symmetries. Further, it is shown that all smooth vector fields tangent to the cross-sections are Hamiltonian. We show that joining two WIHs which differ in these Hamiltonians and boundary data, under the action of a supertranslation, necessarily require the inclusion of an intermediate dynamical phase, possibly with the inclusion of a stress energy tensor. This phase of the boundary is non-expanding but not a WIH and invariably leads to a violation of the dominant energy condition. The assumptions made allow us to reconstruct the (classically) pathological stress energy tensor also.

gr-qc↗