arXiv subjects

K. K. Sharma

Publications and source records attributed to K. K. Sharma.

7 recordsLinked to original sources

arXiv2026

Quasinormal modes of the generalized JMN naked singularity using exact WKB analysis

In this paper, we study the quasinormal modes of the generalized Joshi-Malafarina-Narayan (JMN) naked singularity spacetime using the exact Wentzel-Kramers-Brillouin (WKB) method. Working in the complex radial plane, we construct the exact WKB momentum function, determine its turning points, and compute the associated Stokes geometry for representative quasinormal mode (QNM) frequencies. We obtained a bow-shaped deformation of Stokes curves on the side of the complex plane containing the central singularity in JMN spacetime. We show analytically that this structure originates from the logarithmic branch-point singularity of the WKB phase at $(r = 0)$, which is absent in Schwarzschild spacetime. This establishes the bow-shaped Stokes topology as a direct signature of the naked singularity in the global analytic structure of the perturbation equation. Our results demonstrate that exact WKB analysis provides a powerful framework for probing the analytic structure of compact objects, and suggest that topological features of Stokes geometry may offer a new avenue for distinguishing black holes from horizonless alternatives.

gr-qc↗

arXiv2012

On the optical properties of Ag^{+15} ion-beam irradiated TiO_{2} and SnO_{2} thin films

The effects of 200-MeV Ag^{+15} ion irradiation on the optical properties of TiO_{2} and SnO_{2} thin films prepared by using the RF magnetron sputtering technique were investigated. These films were characterized by using UV-vis spectroscopy, and with increasing irradiation fluence, the transmittance for the TiO_{2} films was observed to increase systematically while that for SnO_{2} was observed to decrease. Absorption spectra of the irradiated samples showed minor changes in the indirect bandgap from 3.44 to 3.59 eV with increasing irradiation fluence for TiO_{2} while significant changes in the direct bandgap from 3.92 to 3.6 eV were observed for SnO_{2}. The observed modifications in the optical properties of both the TiO_{2} and the SnO_{2} systems with irradiation can be attributed to controlled structural disorder/defects in the system.

cond-mat.mtrl-sci↗

arXiv2011

Model Independent Constraints on Solar Neutrinos

Using the data from SNO NCD phase, SuperK, Borexino and KamLAND Solar phase, we derive in a model independent way, bounds on the possible components in the solar neutrino flux. We update the limits on the antineutrino ($\barν_x$) flux and sterile ($ν_s$) component and compare them with the previous results obtained using SNO Salt phase data and data from SuperKamiokande experiments. It is affirmed that the upper bound on $\barν_x$ is independent of the $ν_s$ component. We recover the $ν_s$ and $\barν_x$ upper bounds existing in the literature. We also obtain bounds on $f_B$, the SSM normalization factor and the common parameter range for $f_B$ and the $ν_s$ components in the light of latest data. In summary, we update, in a model independent way, the previous results existing in literature in the light of latest solar neutrino data.

hep-ph↗

arXiv1998

A Study of Weak Mesonic Decays of $Λ_c$ and $Ξ_c$ Baryons on the Basis of HQET Results

We investigate two-body Cabibbo-angle enhanced weak decays of charmed baryons into octet baryon and pseudoscalar meson in the current algebra framework with inclusion of the factorization terms which are evaluated using the HQET guided baryonic form factors. We obtain the branching ratios and asymmetry parameters for various Cabibbo-enhanced decays of $Λ_c^+$, $Ξ_c^+$ and $Ξ_c^0$ baryons. Sensitivity of the flavor dependence of the spatial wavefunction overlap on the branching ratios and asymmetry parameters is also investigated.

hep-ph↗

arXiv1998

Rare Decays of ψand Υ

We study two-body weak hadronic decays of ψand Upsilon employing the factorization scheme. Branching ratios for ψ-> PP/PV and Υ-> PP/PV decays in the Cabibbo-angle-enhanced and Cabibbo-angle-suppressed modes are predicted.

hep-ph↗

arXiv1997

SU(3)_flavor analysis of two-body weak decays of charmed baryons

We study two-body weak decays of charmed baryons Λ_c and Ξ_c into an octet or decuplet baryon and a pseudoscalar meson employing the SU(3) flavor symmetry. Using certain measured Cabibbo-favored modes, we fix the reduced amplitudes and predict the branching ratios of various decays of charmed baryons in the Cabibbo-enhanced, -suppressed and -doubly suppressed modes.

hep-ph↗

arXiv1995

Nonfactorizable contributions to weak $D \to PV$ decays

We investigate nonfactorizable contributions to two-body hadronic decays of the charmed mesons to a pseudoscalar meson and a vector meson in Cabibbo-favored mode. Employing SU(3)-flavor symmetry for the nonfactorizable matrix elements, we obtain branching ratios of the decays in consistent agreement with experiment.

hep-ph↗