arXiv subjects

P. C. Vinodkumar

Publications and source records attributed to P. C. Vinodkumar.

At least 19 recordsLinked to original sources

arXiv2025

Impact of Anisotropy on Neutron Star Structure and Curvature

We investigate the impact of pressure anisotropy on the structural and geometric properties of neutron stars within general relativity, focusing primarily on the phenomenological Bowers-Liang (BL) model, and comparing selected results with a quasi-local prescription. Using the SLy equation of state, we explore how anisotropic stresses modify global observables such as the mass-radius relation, moment of inertia, compactness, and tidal deformability over a broad range of anisotropy parameters. We find that moderate positive anisotropy can increase the maximum supported mass up to approximately $2.4\;M_\odot$ and enhance stellar compactness by up to $20\%$ relative to isotropic configurations, while remaining broadly consistent with current NICER and gravitational-wave constraints. To probe the internal gravitational field, we compute curvature invariants including the Ricci scalar, the Ricci tensor contraction, the Kretschmann scalar, and the Weyl scalar. We show that curvature measures directly tied to the matter distribution exhibit a strong sensitivity to anisotropy, whereas the Weyl curvature remains comparatively insensitive, reflecting its role as a measure of the free gravitational field. Within the phenomenological BL framework, the maximum compactness increases with anisotropy and reaches values as high as $\mathcal{C}_{\max}\approx 0.25$-$0.38$ for $\lambda_{\rm BL}\in[-4,+4]$, although the physical realizability of such highly compact configurations depends sensitively on the underlying anisotropy mechanism. A comparison with the quasi-local model highlights the strong model dependence of anisotropic effects, underscoring both the potential significance and the limitations of phenomenological anisotropy prescriptions in modeling strong-field neutron-star interiors.

gr-qc↗

arXiv2023

Relativistic stellar modeling with perfect fluid core and anisotropic envelope fluid

We investigate the effect of density perturbations and local anisotropy on the stability of stellar matter structures in general relativity using the concept of cracking. Adopting a core-envelope model of a super-dense star, we examine the properties and stability conditions by introducing anisotropic pressure to the envelope region. Furthermore, we propose self-bound compact stars with an anisotropic envelope as a potential progenitor for starquakes. We show how the difference between sound propagation in radial and tangential directions would be used to identify potentially stable regions within a configuration. Due to an increase in the anisotropic parameter, strain energy accumulates in the envelope region and becomes a potential candidate for building-up quake like situation. This stress-energy stored in the envelope region that would be released during a starquake of a self-bound compact star is computed as a function of the magnitude of anisotropy at the core-envelope boundary. Numerical studies for spherically asymmetric compact stars indicate that the stress-energy can be as high as $10^{50}$ erg if the tangential pressure is slightly more significant than the radial pressure. It is happened to be of the same order as the energy associated with giant $\gamma$-ray bursts. Thus, the present study will be useful for the correlation studies between starquakes and GRBs.

gr-qc↗

arXiv2021

Distinct Classes of Compact Stars Based On Geometrically Deduced Equations of State

We have computed the properties of compact objects like neutron stars based on equation of state (EOS) deduced from a core-envelope model of superdense stars. Such superdense stars have been studied by solving the Einstein's equation based on pseudo-spheroidal and spherically symmetric space-time geometry. The computed star properties are compared with those obtained based on nuclear matter equations of state. From the mass-radius ($M-R$) relationship obtained here, we are able to classify compact stars in three categories: (i) highly compact self -bound stars that represents exotic matter compositions with radius lying below 9 km (ii) normal neutron stars with radius between 9 to 12 km and (iii) soft matter neutron stars having radius lying between 12 to 20 km. Other properties such as Keplerian frequency, surface gravity and surface gravitational redshift are also computed for all the three types. The present work would be useful for the study of highly compact neutron like stars having exotic matter compositions.

gr-qc↗

arXiv2020

Masses of tetraquark states in the hidden charm sector above $D-D^*$ threshold

In the diquark-diantiquark composition, we study the masses of hidden charm tetraquark systems ($cq\bar{c}\bar{q}$, $cs\bar{c}\bar{s}$ and $cs\bar{c}\bar{q}$) using a linear confinement potential. In this study, we have factorized the four body system into three subsequent two body systems. To remove degeneracy in the S and P wave masses of mesons and tetraquark states, the spin-spin, spin orbit and tensor components of the confined one gluon exchange interactions are employed. In this attempt, we have been able to assign the $ψ(4230)$ as pure $cq\bar{c}\bar{q}$ tetraquark state. $ψ(4360)$ and $ψ(4390)$ as pure $cs\bar{c}\bar{q}$ tetraquark states. According to our analysis $ψ(4260)$ is an admixture of $^1P_1$ and $^5P_1$ $cq\bar{c}\bar{q}$ tetraquark state. Additionally, we have been able to predict the radiative decay width $Γ_{(ψ\rightarrow J/ψγ)}$, leptonic decay width $Γ_{e^+e^-}$ and hadronic decays of $1^{--}$ tetraquark stat

hep-ph↗

arXiv2017

Excited State Mass spectra and Regge trajectories of Bottom Baryons

We present the mass spectra of radial and orbital excited states of singly heavy bottom baryons; $Σ_{b}^{+}, Σ_{b}^-, Ξ_b^-, Ξ_b^0, Λ_b^0$ and $Ω_b^-$. The QCD motivated hypercentral quark model is employed for the three body description of baryons and the form of confinement potential is hyper coulomb plus linear. The first order correction to the confinement potential is also incorporated in this work. The semi-electronic decay of $Ω_b$ and $Ξ_b$ are calculated using the spectroscopic parameters of the baryons. The computed results are compared with other theoretical predictions as well as with the available experimental observations. The Regge trajectories are plotted in (n, $M^2$) plane.

nucl-th↗

arXiv2016

Mass spectra and Regge trajectories of $Λ_{c}^{+}$, $Σ_{c}^{0}$, $Ξ_{c}^{0}$ and $Ω_{c}^{0}$ Baryons

We calculate the mass spectra of the singly charmed baryons ($Λ_{c}^{+}$, $Σ_{c}^{0}$, $Ξ_{c}^{0}$ and $Ω_{c}^{0}$) using Hypercentral constituent quark model(hCQM). The hyper color coloumb plus linear potential is used to calculate the masses of positive(upto $J^{p}=\frac{7}{2}^{+}$) and negative parity(upto $J^{p}=\frac{9}{2}^{-}$) excited states. The spin-spin, spin-orbital and tensor interaction terms are also incorporated for mass spectra. We have compared our results with other theoretical predictions and Lattice QCD for each baryons. Moreover, the known experimental results are also reasonably closed to our predicted masses. By using the radial and orbital excitation, we construct Regge trajectories for the baryons in (n,$M^{2}$) plane and find their slopes and intercepts. The other properties like, magnetic moments, radiative transitions and radiative decay widths of these baryons are also calculated successfully.

nucl-th↗

arXiv2016

Magnetic Moments of Baryons containing all heavy quarks in Quark-Diquark Model

The triply heavy flavour baryons are studied using the Quark-diquark description of the three-body system. The confinement potential for present study of triply heavy flavour baryons is assumed as coulomb plus power potential with power index $ν$. We have solved Schrodinger equation numerically to calculate the masses of triply heavy flavour baryons. The masses and magnetic moments of triply heavy flavour baryons are computed for different power indices, $ν$, starting from 0.4 to 1.0. The predicted masses and magnetic moments are in good agreement with other theoretical predictions.

hep-ph↗

arXiv2016

Excited State Mass spectra of Singly Charmed Baryons

Mass spectra of excited states of the singly charmed baryons are calculated using the hypercentral description of three body system. The baryon consist of a charm quark and light quarks (u, d and s) are studied in the framework of QCD motivated constituent quark model. The form of confinement potential is hyper coloumb plus power potential with potential index $ν$, varying from 0.5 to 2.0. The first order correction to the confinement potential is also incorporated in this approach. The radial as well as orbital excited state masses of $Σ_{c}^{++}, Σ_{c}^+, Σ_{c}^0, Ξ_c^+, Ξ_c^0, Λ_c^+, Ω_c^0$ baryons, are reported in this paper. We have incorporated spin-spin, spin-orbit and tensor interactions perturbatively in the present study. The semi-electronic decay of $Ω_c$ and $Ξ_c$ are also calculated using the spectroscopic parameters of these baryons. The computed results are compared with other theoretical predictions as well as with the available experimental observations. We also construct the Regge trajectory in ($n_r$, $M^{2}$) and (J, $M^{2}$) plane for these baryons.

hep-ph↗

arXiv2016

Screening Effects on the Binding Energy and Stability of Quarkonia States

We have studied the thermal stability of Quarkonia states by computing the effects of color-screening and vacuum screening based on a temperature dependent screened coulomb plus power potential for the quark-antiquark interaction. Medium effects on the properties of charmonia and bottomonia states are studied. The color screening and the vacuum screening effects on the stability of the quarkonia states are also separately calculated for comparison.

hep-ph↗

arXiv2015

Decay rates of charmonia within a quark-antiquark confining potentials

In this work, we investigate the spectroscopy and decay rates of charmonia within the framework of non-relativistic Schrödinger equation by employing an approximate inter quark-antiquark potential. The spin hyperfine, spin-orbit and tensor components of the one gluon exchange interaction are employed to compute the spectroscopy of the excited S states and few low-lying P and D waves. The resultant wave functions at zero inter quark separation as well as some finite separation are employed to predict the di-gamma, di-leptonic and di-gluon decay rates of charmonia states by using the conventional Van Royen-Weisskopf formula. The di-gamma and di-leptonic decay widths are also computed by incorporating the relativistic corrections of order $v^4$ within the NRQCD formalism. We have observed that the NRQCD predictions with their matrix elements computed at finite radial separation yielded results which are found to be in better agreement with experimental value for both di-gamma and di-leptonic decays. The same scenario is seen in the case when di-gamma and di-leptonic decay widths are computed with Van Royen-Weisskopf formula. It is also observed that the di-gluon decay width with the inclusion of binding energy effects are in better agreement with the experimental data available for 1S-2S and 1P. The di-gluon decay width of 3S and 2P waves waves are also predicted. Thus, the present study of decay rates clearly indicates the importance of binding energy effects.

hep-ph↗

arXiv2015

Mass spectra and decay properties of $D$ Meson in a relativistic Dirac formalism

The mass spectra of $D$ meson states are calculated in the framework of a relativistic independent quark model. For the present study, we have used the martin like potential for the quark confinement. Our predicted states in S-wave, $2\ ^3S_1$ (2605.86 MeV) and $2\ ^1S_0$ (2521.72 MeV) are in very good agreement with experimental result of $2608\pm{2.4}\pm{2.5}$ MeV and $2539.4\pm{4.5}\pm{6.8}$ MeV respectively reported by BABAR Collaboration. The calculated P-wave $D$ meson states, $1^3P_2$ (2468.22 MeV), $1^3P_1$ (2404.94 MeV), $1^3P_0$ (2315.24 MeV) and $1^1P_1$ (2367.94 MeV) are in close agreement with experimental average (Particle Data Group) values of $2462.6 \pm 0.7 $ MeV, $2427 \pm 26 \pm 25$ MeV, $2318 \pm 29 $ MeV and $2421.3 \pm 0.6 $ MeV respectively. The pseudoscalar decay constant ($f_P$= 202.57 MeV) of $D$ meson obtained using this relativistic formalism is in very good agreement with the experiment as well as with the lattice and other available theoretical predictions. The Cabibbo favoured hadronic decay branching ratios, BR$(D^0\rightarrow K^- π^+)$ as $3.835 \%$ and BR $(D^0\rightarrow K^+ π^-)$ as $1.069 \times 10^{-4} $ are also in very good agreement with the respective experimental values of $ 3.91 \pm 0.08\%$ and $(1.48\pm 0.07) \times 10^{-4}$ reported by CLEO Collaboration. Our predicted results in leptonic decay widths of $D$ meson are also in better accord with experiment as well as other theoretical results. The mixing parameters of $D^0 - \bar{D}^0$ oscillation, $x_q$ (5.14 $\times 10^{-3}$), $y_q$ (6.02 $\times 10^{-3}$) and $R_M$ (3.13 $\times 10^{-5}$) are in very good agreement with BaBar and Belle Collaboration results.

hep-ph↗

arXiv2014

Study of Bose-Einstein condensation using generalized canonical partition function

We open a new discussion of generalized canonical partition function in standard statistical mechanics and apply it for the study of Bose-Einstein condensation. We discuss the possible cases for the generalized canonical partition function and arrives at a conclusion that the system of trapped bose gas will not be existing at absolute zero. We analyse the present study with an experimental result and point out the general difficulties in the analyses of experimental observations, which can possibly suppress the effect of generalized canonical partition function over standard canonical partition function. We mention that the experimental studies with ideal condensates at absolute zero with an unbiased approach towards the traditional Bose-Einstein condensation theory can bring out the effect of generalized canonical partition function.

cond-mat.quant-gas↗

arXiv2013

Spectroscopy of di-meson bound states in charm and beauty sector

Using the Woods Saxon plus Coulomb type of interaction between two hadron molecules, we have calculated the binding energies and masses of the tetraquark states such as $D\bar{D}$, $D\bar{D}^*$, $D^*\bar{D}^*$, $D^+\bar{D}^*$ in the charm sector and $B\bar{B}$, $B^*\bar{B}^*$, $B\bar{B}^*$ in the bottom sector.

hep-ph↗

arXiv2012

Medium effects on the quarkonia states above critical temperature

We present the quarkonia correlators for charmonium and bottomonium systems in the pseudoscalar, vector and scalar channels. For the description of quark-antiquark interaction we adopt the temperature dependant colour screening potential of the power law form. The spectroscopic parameters defined from the model are employed in the spectral functions to compute the quarkonia correlators. We find considerable medium modifications to the effective masses of the quarkonia as well as in the behaviour of the respective radial wave functions. These modifications are then reflected in the computed correlators. The general behaviour of correlators in the vector and scalar channel are in accordance with the latest lattice results while their behaviour in the pseudoscalar channels are found to be different.

hep-ph↗

arXiv2012

Electromagnetic transition properties of $Δ\rightarrow Nγ$ in a hypercentral scheme

The electromagnetic transition properties of the decuplet to octet baryon ($Δ\rightarrow Nγ$) is studied within the frame work of a hypercentral quark model. The confinement potential is assumed as hypercentral coloumb plus linear potential. The transition magnetic moment and transition amplitude $f_{M_1}$ for the $Δ\rightarrow Nγ$ are in agreement with other theoretical predictions. The present result of the radiative decay width is found to be in excellent agreement with the experimental values reported by the particle data group over other theoretical model predictions.

hep-ph↗

arXiv2012

Leptonic and Digamma decay Properties of S-wave quarkonia states

Based on Martin like potential, the S-wave masses of quarkonia have been reviewed. Resultant wave functions at zero inter quark separation are employed to compute the hyperfine splitting of the nS states and the leptonic and digamma decay widths of $n{^3S_1}$ and $n{^1S_0}$ states of quarkonia respectively. Analysis on the level differences of S-wave excited states of quantum mechanical bound systems show a systematic behaviour as n-increases. In view of such systematic behaviour expected for quarkonia, we observe that Y(4263) and X(4630) $1^{--}$ states are closer to the 4S and 6S states while $ψ(4415)$ and Z(4430) are closer to the 5S state of $c\bar{c}$ systems. Similarly we find $Υ(10865)$ is not fit to be the 5S state of $b\bar{b}$ system. while $Y_b (10880)$ observed by Belle or (10996) observed by Babar fit to be the 6S state of bottonia. Our predicted leptonic width, 0.242 keV of $Υ(10579, 4S)$ is in good agreement with the experimental value of 0.272 $\pm$ 0.029 keV. We predict the leptonic widths of the pure 5S and 6S states of upsilon states as 0.191 keV and 0.157 keV respectively. In the case of charmonia, we predict the leptonic widths of the 4S, 5S and 6S states as 0.654 keV, 0.489 keV and 0.387 keV respectively.

hep-ph↗

arXiv2011

Properties of Light Flavour Baryons in Hypercentral quark model

The light flavour baryons are studied within the quark model using the hyper central description of the three-body system. The confinement potential is assumed as hypercentral coulomb plus power potential ($hCPP_ν$) with power index $ν$. The masses and magnetic moments of light flavour baryons are computed for different power index, $ν$ starting from 0.5 to 1.5. The predicted masses and magnetic moments are found to attain a saturated value with respect to variation in $ν$ beyond the power index $ν>$ 1.0. Further we computed transition magnetic moments and radiative decay width of light flavour baryons. The results are in good agreement with known experimental as well as other theoretical models.

hep-ph↗

arXiv2011

Spectroscopy and decay properties of $Σ_{b}, Λ_{b}$ baryons in quark-diquark model

Properties of single beauty baryons ($Σ_{b},Λ_{b}$) are studied based on the quark-diquark structure. The confinement potential is assumed as two body colour coulomb plus power potential with exponent $ν$. We find a strong correlation between the choice of the heavy quark mass parameter ($m_{b}$), strong coupling constant ($α_{s}$) and the potential exponent ($ν$) for getting the experimental mass spilt of $m_{Σ^{*}_{b}}- m_{Σ_{b}}=21.2\pm2.0 $ MeV. The resultant spectroscopic parameters are used for computing magnetic moments, the electromagnetic radiative decay, strong hadronic decay and semileptonic decay widths of $Σ_{b}, Λ_{b}$ systems. Our predictions on the radiative decay width correspond to $Σ^{*0}_{b}\rightarrowΛ_{b}γ$ are in agreement with the QCD sum rule prediction. The present results on the semileptonic decay widths of $Λ_{b}\rightarrow Λ_{c}lν_{l}$ (2.50-4.73) $ *10^{10} s^{-1}$ are in agreement with the experimental value of $3.59^{+1.234}_{-0.936} *10^{10} s^{-1}$ reported by (PDG 2010).

hep-ph↗