arXiv subjects

Arindam Kumar Chatterjee

Publications and source records attributed to Arindam Kumar Chatterjee.

6 recordsLinked to original sources

arXiv2026

Energy Extraction and Particle Acceleration in String-Inspired Rotating Einstein-Maxwell-Dilaton-Axion Black Hole

We study energy extraction and particle acceleration in the rotating Einstein-Maxwell-Dilaton-Axion (EMDA) black hole, focusing on the impact of dilaton hair $b\le 0$ on near-horizon energetics relative to Kerr. For the Penrose process we derive analytic expressions for the maximum efficiency and show that negative $b$ can strongly enhance the ideal gain in the extremal regime (e.g., reaching $\sim 91\%$ for $b=-0.3$). We then compute the irreducible mass $M_{\rm irr}$ and the corresponding rotationally extractable energy $\mathcal{E}_{\rm rot}\equiv M-M_{\rm irr}$, finding that $M_{\rm irr}$ decreases monotonically as $b$ becomes more negative while $\mathcal{E}_{\rm rot}$ increases, indicating a larger spin-energy reservoir; at extremality the extracted share from rotation is $\mathcal{E}_{\rm rot}/M\simeq 0.63$ for EMDA, reducing to the Kerr value $\simeq 0.29$ at $b=0$. Kinematic constraints relevant to fragment production are quantified via the Wald and Bardeen--Press--Teukolsky bounds, which are progressively relaxed for more negative $b$. For wave superradiance we obtain the flux balance and the amplification window $0<\beta<k\Omega_H$, with $\Omega_H$ expressed through $\Xi=r_H^{2}+2br_H+a^{2}$; negative $b$ modifies $\Omega_H$ and enlarges the parameter region exhibiting negative horizon flux. Finally, we analyse two-particle collisions and derive $E_{\rm cm}$, showing that the Ba\~nados--Silk--West divergence persists at the horizon when one particle is tuned to the critical angular momentum $L_c=E/\Omega_H$, while $E_{\rm cm}$ remains finite for generic angular momenta. Overall, dilaton hair in EMDA simultaneously amplifies energy-extraction channels and reshapes the near-horizon thresholds governing high-energy collisions.

gr-qc↗

arXiv2026

Inertial Frame Dragging as a Probe to Differentiate Kerr-Newman Naked Singularities from Black Holes

We study the spin precession of a test gyroscope attached to a stationary observer in Kerr-Newman spacetime to distinguish a naked singularity from a black hole. Extending earlier work on Kerr, we examine how the electric charge $Q$ affects precession in both cases. For gyroscopes with nonzero angular velocity $\Omega$, we derive closed-form expressions for the general spin-precession, Lense-Thirring, and geodetic precession frequencies. For Kerr-Newman black holes, the spin-precession frequency generically diverges as the event horizon is approached from any direction, remaining finite only for zero-angular-momentum observers (ZAMOs). By contrast, for Kerr-Newman naked singularities, it remains finite everywhere except at the ring singularity on the equatorial plane. We show that $Q$ systematically modifies these features, especially in rapidly rotating regimes, and that the acceleration scalar further sharpens the black hole/naked singularity distinction. We also investigate the Lense-Thirring (nodal) precession frequency of equatorial circular orbits in accretion disks. For black holes, the nodal frequency decreases monotonically with radius, whereas for naked singularities it rises, attains a finite maximum, and then decreases; for sufficiently large spin and charge it can even change sign, signalling a reversal of the precession direction. We further compute the Keplerian, radial, and vertical epicyclic frequencies, along with the periastron precession frequency, highlighting the role of $Q$ in the ISCO and the orbital-frequency hierarchy. Since these frequencies are closely related to observed quasiperiodic oscillations (QPOs), these features provide a strong-field probe of whether a rotating compact object is a black hole or a naked singularity.

gr-qc↗

arXiv2021

Optical and Thermodynamic Properties of a Rotating Dyonic Black Hole Spacetime in $\mathcal{N} = 2, U(1)^2$ gauged supergravity

The null geodesics and the distance of closest approach for photon around a rotating dyonic black hole in $\mathcal{N} = 2, U(1)^2$ gauged supergravity is studied. The phenomenon of black hole shadows with various black hole parameters has also analyzed. Further, the investigation of various thermodynamic properties for this black hole is performed with various thermodynamic parameters at the horizon. The heat capacity to study the thermodynamic stability of this black hole spacetime is also studied. The influence for different values of the black hole parameters $ ν$, $ e $, $ ν$, $ g $ and $N_{g}$ on the phenomenon of black hole shadows and thermodynamic parameters is also investigated visually.

gr-qc↗

arXiv2019

Analytic solutions of the geodesic equation for Reissner-Nordström-(anti-)de Sitter black holes surrounded by different kinds of regular and exotic matter fields

The purpose of this study is the derivation of the equation of motion for particles and light in the spacetime of Reissner-Nordström-(anti-)de Sitter black holes in the background of different kinds of regular and exotic matter fields. The complete analytical solutions of the geodesic equations are given in terms of the elliptic Weierstraß $\wp$-function and the hyperelliptic Kleinian $σ$-function. Finally after analyzing the geodesic motion of test particles and light using parametric diagrams and effective potentials, we present a list of all possible orbits.

gr-qc↗

arXiv2019

A sincere tribute to E.C.G Sudarshan's phenomenal contribution toward quantum theory of optical coherence

The diagonal representation and optical equivalence theorem are the E. C. G. Sudarshan's mid 20th century adventures in non-classical optics. It basically deals with a quantum mechanical description of photons to explain the quantum properties of light. Inspired by Sudarshan's pioneering work we try to explain the every minute mathematical details of his paper "Equivalence of semi-classical and quantum mechanical descriptions of statistical light beams". In this article we are going to go through some of the basics in developing quantum optics, then land up in E.C.G's original work and try to present it as rigorous as possible. We show some of its important applications in various classes of physics problems.

physics.hist-ph↗

arXiv2019

Energy extraction and particle acceleration around a rotating dyonic black hole in $N=2$, $U(1)^2$ gauged supergravity

In the present paper, we explore various gravitational aspects such as energy extraction (via the Penrose process and Superradiance), particle collisions around a $\mathcal{N}=2$, $U(1)^2$ dyonic rotating black hole (BH) in the gauged supergravity model. The impact of the rotation parameter ($a$) and the gauge coupling constant ($g$) on the behaviour of horizon and ergoregion of the BH is studied. It is of interest to note that, compared with the extremal Kerr BH, the gauge coupling constant, under certain constraints, can enhance the maximum efficiency of energy extraction by the Penrose process almost double. Under the same constraints, we can extract approximately 60.75\% of the initial mass energy from the BH which is noticeably higher in contrast to the extremal Kerr BH. The limit of energy extraction in terms of the local speeds of the fragments is also examined with the help of the Wald inequality. We identify an upper limit on the gauge coupling constant up to which the phenomenon of Superradiance is likely to occur. Finally, we computed the center-of-mass energy ($E_{CM}$) of two particles with the same rest masses moving in the equatorial plane of the BH. Our study also aims to sensitize $E_{CM}$ to the rotation parameter and the gauge coupling constant for extremal and nonextremal spacetime as well. Especially, for the extremal case, an infinitely large amount of $E_{CM}$ can be achieved closer to the horizon which allows the BH to serve as a more powerful Planck-energy-scale collider as compared to Kerr and any other generalized BHs in the Kerr family explored so far in general relativity. However, $E_{CM}$ for the nonextremal spacetime is shown to be finite and has an upper bound.

gr-qc↗