arXiv subjects

K. Hari

Publications and source records attributed to K. Hari.

7 recordsLinked to original sources

arXiv2026

The Gravitational Spectral Radio Forest: A Signature of Primordial Black Holes

We propose a novel gravitational signature to detect Primordial Black Hole (PBH) dark matter by treating interstellar hydrogen as a quantum sensor for spacetime curvature. Focusing on H II regions, we demonstrate that the Riemann tidal tensor of an \emph{asteroid-mass} PBH induces a symmetric splitting of the $2P_{3/2}$ state in bound hydrogen atoms. This relativistic effect redistributes $9.9\,\mathrm{GHz}$ absorption line into a gravitational spectral radio forest with a bandwidth $\sim 2\,\mathrm{GHz}$. By accounting for active accretion of Hydrogen atoms and the resulting density-squared emission measure within the Bondi radius, we find a relatively enhanced absorption spectrum. This feature presents a concrete, high-contrast target for upcoming radio-surveys to constrain PBH populations in the dark matter sector.

gr-qc↗

arXiv2026

Gravitational wave detection via photon-graviton scattering and quantum interference

We present a fully quantum field-theoretic framework for gravitational wave (GW) detection in which the interaction is described as photon-graviton scattering. In this picture, the GW acts as a coherent background that induces inelastic energy exchanges with the electromagnetic field - analogous to the Stokes and anti-Stokes shifts in Raman spectroscopy. We propose a detection scheme sensitive to this microscopic mechanism based on Hong-Ou-Mandel interference. We show that the scattering-induced phase shifts render frequency-entangled photon pairs distinguishable, spoiling their destructive quantum interference. GW signal is thus encoded in the modulation of photon coincidence rates rather than classical field intensity, offering a complementary quantum probe of the gravitational universe that recovers the standard classical response in the macroscopic limit.

gr-qc↗

arXiv2025

Twin-paradox and Entanglement

We study the quantum version of the classical twin paradox in special relativity by replacing the twins with quantum detectors, and studying the transitions and entanglement induced by coupling them to a quantum field. We show that the \textit{changes} in direction of acceleration leave imprints on detector responses and entanglement, inducing novel features which might have relevance in black hole spacetimes.

gr-qc↗

arXiv2025

Radiative process of tripartite entangled probes in inertial motion

We study the radiative process of three entangled quantum probes initially prepared in a tripartite W state. As a basic set-up, we consider the probes to be inertial in flat spacetime and investigate how the radiative process is affected by different probe configurations. We take the quantum probes as either static or moving with uniform velocities and consider different switching scenarios. Our main observation confirms that the radiative process depends distinctively on the initial configuration in which the probes are arranged, as well as on the direction of the probe velocity. We also extend our analysis to a thermal environment, thereby simulating a more realistic background. We thoroughly discuss the effects due to different switchings, the thermal background, and probe motion on the radiative process of these tripartite entangled probes. We also comment on how the observations from this work can help prepare a set-up least affected by quantum decoherence.

gr-qc↗

arXiv2025

Entanglement between accelerated probes in a de Sitter spacetime

We initiate an investigation into features of vacuum entanglement as probed by accelerated quantum probes in curved spacetime. Focussing specifically on de Sitter (dS) spacetime with curvature $\Lambda$, we obtain several exact results corresponding to different kinematical set-up of the probes. The interaction with the quantum field creates a non-local correlation between initially uncorrelated probes accelerating in different directions. It is well known that a single quantum probe in dS spacetime with uniform acceleration $a$ responds exactly as a quantum probe in Minkowski spacetime with "effective" acceleration $q \equiv\sqrt{a^2+\Lambda}$. However, no such mapping generically exists for the entanglement between probes. Our results suggest that entanglement exhibits independent variations with changes in acceleration and curvature depending on different configurations of detector motion.

gr-qc↗

arXiv2019

Dissipative optical solitons in asymmetric Rosen-Morse potential

We investigate the existence and stability of dissipative soliton solution in a system described by complex Ginzburg-Landau (CGL) equation with asymmetric complex potential, which is obtained from original parity reflection - time reversal ($\mathcal{PT}$) symmetric Rosen-Morse potential. In this study, stability of solution is examined by numerical analysis to show that solitons are stable for some parameter ranges for both self-focusing and self-defocusing nonlinear modes. Dynamical properties such as evolution and transverse energy flow for both modes are also analyzed. Obtained results are useful for experimental designs and applications in related fields.

nlin.PS↗

arXiv2018

Optical solitons in near $\mathcal{PT}-$symmetric Rosen-Morse potential

We investigate the existence of stable soliton solution in a system described by complex Ginzburg-Landau (CGL) equation with near parity reflection - time reversal ($\mathcal{PT}$) symmetric Rosen-Morse potential. In this study, the stability of solution is examined by numerical analysis to show that solitons are stable for some parameter ranges. The dynamical properties such as evolution and transverse energy flow for both self-focusing and self-defocusing nonlinear mode are also analyzed. The obtained results are useful for experimental designs and applications in related fields.

nlin.PS↗