arXiv subjects

S. K. Biswal

Publications and source records attributed to S. K. Biswal.

At least 19 recordsLinked to original sources

arXiv2025

Investigating the correlations of bulk properties of hyperon star with dark matter

The strong gravitational pull of the neutron star leads to the accretion of dark matter (DM) inside the core of the neutron star. The accretion of DM affects the bulk properties of the neutron star. Here, we study how the accretion of WIMP (Weakly Interacting Massive Particles) dark matter particles affects the $Δ-$admixed hyperon star's bulk properties specifically mass, radius, tidal deformability, $f-$mode frequency and moment of inertia. The inclusion of dark matter softens the EOS (equation of state) and reduces the maximum possible mass, canonical radius, canonical tidal deformability, and moment of inertia of canonical star. However, the $f-$mode frequency of the canonical star increases. We find a cubical correlation between the dark matter fermi momenta $k_f^{DM}$ and bulk properties of canonical star.

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arXiv2025

Correlation between the curvature and some properties of the neutron star

According to the general theory of relativity, a massive body induces curvature in the surrounding spacetime. In this study, the surface curvature (SC) of neutron stars is computed using various curvature quantities derived from the relativistic mean-field, density-dependent RMF, and Skyrme-Hartree-Fock equations of states. Neutron star properties, including mass, radius, compactness, and central density, are calculated utilizing the Tolman-Oppenheimer-Volkoff equations. The analysis reveals a significant cubic correlation between the SC and compactness for the canonical 1.4 $M_{\odot}$ neutron star, with a correlation coefficient of 0.99, indicating an almost linear relationship. A similarly significant inverse cubic correlation is observed between the SC and the radius of the canonical star. However, these correlations diminish for the maximum mass NS. Furthermore, a universal relation between the SC and the dimensionless tidal deformability ($Λ$) for the canonical neutron star is established. Using the tidal deformability constraint of GW170817 ($Λ_{1.4} = 190_{-120}^{+390}$), the surface curvature is limited to SC$_{1.4} (10^{14}) = 2.87^{+0.30}_{-0.78}$ at a confidence level 90\%. Furthermore, the tidal deformability constraint of the secondary component in the GW190814 event ($Λ_{1.4} = 616_{-158}^{+273}$) offers a more stringent limit, with the result of SC$_{1.4} (10^{14}) = 2.03^{+0.27}_{-0.36}$. These findings indicate that the GW190814 event imposes more rigorous constraints on SC compared to GW170817.

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arXiv2025

Exploring the impact of $Δ$-isobars on Neutron Star

We include the $Δ$-isobars in the equation of state (EOS) of neutron star (NS) and study its effects with various parameter sets of the RMF model. We compare our results with the NS's constraints from the mass-radius measurement of PSR J0348+0432, PSR J1614-2230, PSR J0030+0451, PSR J0740+6620, PSR J0952-0607, and tidal deformability of GW170817. We calculate the mass-radius profile and tidal deformabilities of the NS using 21 parameter sets of the RMF model.Analyzing the result with various parameters, it is clear that only few parameter sets can satisfy simultaneously the constraints from NICER and GW170817. NLD parameter set satisfy all the constraints of NICER and GW170817. For its strong predictive power for the bulk properties of the neutron star, we take NLD parameter set as a representative for the detailed calculation of effect of $Δ$-isobar on neutron star properties. We demonstrate that it is possible that $Δ$-isobar can produce at 2-3 times the saturation density by adjusting the coupling constants $X_{σΔ}$, $X_{ρΔ}$ and $X_{ωΔ}$ in an appropriate range. Bulk properties of the NS like mass-radius profile and tidal deformability is strongly affected by the interaction strength of $Δ$-isobar. Our calculation shows that it is also possible that by choosing $X_{σΔ}$, $X_{ρΔ}$ and $X_{ωΔ}$ to a suitable range the threshold density of $Δ^-$-isobar become lower than $Λ^0$ hyperon. For a particular value of $Δ$-coupling constants, the $R_{1.4}$ decrease by 1.7 km. This manuscipt give an argumentative justification for allowing $Δ$-isobar degrees of freedom in the calculation of the NS properties.

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arXiv2021

BigApple force and its implications to finite nuclei and astrophysical objects

The secondary component of the GW190814 event left us with a question, "whether it is a supermassive neutron star or lightest black-hole?". Recently, Fattoyev et al. have obtained an energy density functional (EDF) named as BigApple, which reproduces the mass of the neutron star is 2.60 $M_\odot$ which is well consistent with GW190814 data. This study explores the properties of finite nuclei, nuclear matter, and neutron stars by using the BigApple EDF along with four well-known relativistic mean-field forces, namely NL3, G3, IOPB-I, and FSUGarnet. The finite nuclei properties like binding energy per particle, skin thickness, charge radius, single-particle energy, and two-neutron separation energy are well predicted by the BigApple for a series of nuclei. The calculated nuclear matter quantities such as incompressibility, symmetry energy, and slope parameters at saturation density are consistent with the empirical or experimental values where ever available. The predicted canonical tidal deformability by the BigApple parameter set is well-matched with the GW190814 data. Also, the dimensionless moment of inertia lies in the range given by the analysis of PSR J0737-3039A.

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arXiv2021

Impacts of dark matter on the $f$-mode oscillation of hyperon star

We investigate the $f$-mode oscillation of the dark matter admixed hyperon star within the relativistic Cowling approximation. The macroscopic properties are calculated with the relativistic mean-field equation of states by assuming that the dark matter particles are inside the star. The $f$-mode oscillation frequencies (only for $l=2$) are calculated with four different neutron star equation of states. We also check the effects of hyperons/dark matter and hyperons with dark matter equation of states on the $f$-mode oscillations varying with different astrophysical quantities such as mass ($M$), radius ($R$), compactness ($M/R$), surface red-shift ($Z_s$), average density ($\barρ$), dimensionless tidal deformability ($Λ$) of the neutron star. Significant changes have been seen in the $f$-mode frequencies with and without hyperons/dark matter or hyperons+dark matter. Substantial correlations are observed between canonical frequencies and $Λ$ ($f_{1.4}-Λ_{1.4}$) and maximum frequencies and canonical $Λ$ ( $f_{max}-Λ_{1.4}$).

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arXiv2021

Impacts of dark matter on the curvature of the neutron star

The effects of dark matter (DM) on the curvatures of the neutron star (NS) are examined by using the stiff and soft relativistic mean-field equation of states. The curvatures of the NSs are calculated with the variation of baryon density. Also, it is found that the radial variation of the different curvatures significantly affected by the presence of DM inside the NS. The effects of DM are less pronounced on the compactness of the maximum NS mass, but still significant. The NS surface curvature is found to be more remarkable for the massive star. The binding energy of the NSs become positive with the increasing DM momentum and makes the system unstable.

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arXiv2021

Effects of dark matter on the nuclear and neutron star matter

We study the dark matter effects on the nuclear matter parameters characterising the equation of states of super dense neutron-rich nucleonic-matter. The observables of the nuclear matter, i.e. incompressibility, symmetry energy and its higher-order derivatives in the presence dark matter for symmetric and asymmetric nuclear matter are analysed with the help of an extended relativistic mean-field model. The calculations are also extended to beta-stable matter to explore the properties of the neutron star. We analyse the dark matter effects on symmetric nuclear matter, pure neutron matter and neutron star using NL3, G3 and IOPB-I forces. The binding energy per particle and pressure are calculated with and without considering the dark matter interaction with the nuclear matter systems. The influences of dark matter are also analysed on the symmetry energy and its different coefficients. The incompressibility and the skewness parameters are affected considerably due to the presence of dark matter in the nuclear matter medium. We extend the calculations to the neutron star and find its mass, radius and the moment of inertia for static and rotating neutron star with and without dark matter contribution. The mass of the rotating neutron star is considerably changing due to rapid rotation with the frequency in the mass-shedding limit. The effects of dark matter are found to be important for some of the nuclear matter parameters, which are crucial for the properties of astrophysical objects.

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arXiv2021

Constraining nuclear matter parameters and neutron star observables using PREX-2 and NICER data

We try to constraints some of the nuclear matter parameters such as symmetry energy ($J$) and its slope ($L$) from the recent inferred data of the PREX-2. Other nuclear matter parameters are adopted from {\bf [Phys. Rev. C 85 035201 (2012), Phys. Rev. C 90 055203 (2014)]} papers and the linear correlation among them are checked by using the Pearson's formula. We find the correlation between $J-L$, $K_τ-J$ and $K_τ-L$ with coefficients 0.85, 0.81 and 0.76 respectively. The neutron star properties such as mass and radius are calculated with 50 unified equation of states. The results are consistent with recently observed pulsars and NICER data except few exceptions. From the radii constraints, we find that the new NICER data allows a narrow radius range contrary to a large range of PREX-2 and the old NICER data leaving us an inconclusive determination of the neutron star radius.

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arXiv2020

Warm dense matter and cooling of supernovae remnants

We study the thermal effects on the nuclear matter (NM) properties such as binding energy, incompressibility, free symmetry energy and its coefficients using NL3, G3 and IU-FSU parameter sets of relativistic mean-field models. These models being consistent with the properties of cold NM, have also been used to study the effect of temperature by incorporating the Fermi function. The critical temperature for the liquid-gas phase transition in the symmetric NM is found to be 14.60, 15.37 and 14.50 MeV for NL3, G3 and IU-FSU parameter sets respectively, which is in excellent agreement with previous theoretical and experimental studies. We inspect that the properties related to second differential coefficient of the binding energy and free symmetry energy at saturation density ( i.e. K 0 (n, T ) and Q sym,0) exhibit the contrary effects for NL3 and G3 parameters as the temperature increases. We find that the prediction of saturated curvature parameter ( K sym,0 ) for G3 equation of state at finite temperature favour the combined analysis of K sym,0 for the existence of massive pulsars, gravitational waves from GW170817 and NICER observations of PSR J0030+0451. Further, we investigate the cooling mechanism of newly born stars through neutrino emissivity controlled by direct Urca process and instate some interesting remarks about neutrino emissivity. We also deliberate the effect of temperature on the M-R profile of Proto-Neutron star.

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arXiv2020

Consistent Skyrme parametrizations constrained by GW170817

The high-density behavior of the stellar matter composed of nucleons and leptons under $β$~equilibrium and charge neutrality conditions is studied with the Skyrme parametrizations shown to be consistent (CSkP) with the nuclear matter, pure neutron matter, symmetry energy and its derivatives in a set of $11$ constraints [Dutra {\it et al.}, Phys. Rev. C 85, 035201 (2012)]. The predictions of these parametrizations on the tidal deformabilities related to the GW170817 event are also examined. The CSkP that produce massive neutron stars give a range of $11.86~\mbox{km} \leqslant R_{1.4} \leqslant 12.55~\mbox{km}$ for the canonical star radius, in agreement with other theoretical predictions. It is shown that the CSkP are compatible with the region of masses and radii obtained from the analysis of recent data from LIGO and Virgo Collaboration (LVC). A correlation between dimensionless tidal deformability and radius of the canonical star is found, namely, $Λ_{1.4} \approx 3.16\times10^{-6}R_{1.4}^{7.35}$, with results for the CSkP compatible with the recent range of $Λ_{1.4}=190_{-120}^{+390}$ from LVC. An analysis of the $Λ_1\timesΛ_2$ graph shows that all the CSkP are compatible with the recent bounds obtained by LVC. Finally, the universal correlation between the moment of inertia and the deformability of a neutron star, named as the \mbox{$I$-Love} relation, is verified for the CSkP, that are also shown to be consistent with the prediction for the moment of inertia of the \mbox{PSR J0737-3039} primary component pulsar.

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arXiv2019

Density-dependent van der Waals model under the GW170817 constraint

We propose a density-dependent function for the attractive interaction in the original van der Waals model to correctly describe the flow constraint at the high-density regime of the symmetric nuclear matter. After a generalization to asymmetric nuclear matter, it was also possible to study the stellar matter regime from this new model. The mass-radius relation for neutron stars under $β$-equilibrium is found to agree with recent X-ray observations. The neutron star masses supported against gravity, obtained from some parametrizations of the model, are in the range of $(1.97-2.07)M_{\odot}$, compatible with observational data from the PSR J0348+0432 pulsar. Furthermore, we verify the reliability of the model in predicting tidal deformabilities of the binary system related to the GW170817 neutron star merger event and find a full agreement with the new bounds obtained by the LIGO/Virgo collaboration.

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arXiv2019

Effects of $ϕ_0$-meson on the EOS of hyperon star in the relativistic mean field model

Nuclear effective interactions are considered as a vital tool to guide into the region of the high degree of isospin asymmetry and density. We take varieties of parameter sets of the RMF model to show the parametric dependence of the hyperon star properties. We add $ϕ_0$-meson to $σ$-$ω$-$ρ$ model. The effects of $ϕ_0$-meson on the equation of state and consequently on the maximum mass of the hyperon star are discussed. Due to the inclusion of $ϕ_0$-meson the threshold density of different hyperon production shift to higher density region. The effects of the hyperon-meson coupling constants on the maximum mass and radius of the hyperon stars are discussed.

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arXiv2016

Tidal deformability of neutron and hyperon star with relativistic mean field equations of state

We systematically study the tidal deformability for neutron and hyperon stars using relativistic mean field (RMF) equations of state (EOSs). The tidal effect plays an important role during the early part of the evolution of compact binaries. Although, the deformability associated with the EOSs has a small correction, it gives a clean gravitational wave signature in binary inspiral. These are characterized by various love numbers kl (l=2, 3, 4), that depend on the EOS of a star for a given mass and radius. The tidal effect of star could be efficiently measured through advanced LIGO detector from the final stages of inspiraling binary neutron star (BNS) merger.

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arXiv2016

Quest for magicity in hypernuclei

In present study, we search the lambda magic number in hypernuclei within the framework of relativistic mean field theory (RMF) with inclusion of hyperon-nucleon and hyperon-hyperon potentials. Based on one- and two-lambda separation energy and two-lambda shell gap, 2, 8, 14, 18, 20, 28, 34, 40, 50, 58, 68, 70 and 82 are suggested to be the $Λ$ magic number within the present approach. The weakening strength of $Λ$ spin-orbit interaction is responsible for emerging the new lambda shell closure other than the model scheme. The predicted $Λ$ magic numbers are in remarkable agreement with earlier predictions and hypernuclear magicity quite resembles with nuclear magicity. %Our results also support the nuclear magicity, Our results are supported by nuclear magicity, where neutron number N = 34 is experimentally observed as a magic which is one of the $Λ$ closed shell in our predictions. In addition, the stability of hypernuclei is also examined by calculating the binding energy per particle, where Ni hypernucleus is found to be most tightly bound triply magic system in considered hypernuclei. Nucleon and lambda density distributions are observed and it is found that introduced $Λ$'s have significant impact on total density and reduces the central depression of the core nucleus. Nucleon and lambda mean field potentials and spin-orbit interaction potentials are also observed for predicted triply magic hypernuclei and the addition of $Λ$'s affect the both the potentials to a large extent. The single-particle energy levels are also analyzed to explain the shell gaps for triply magic multi-$Λ$ hypernuclei.

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arXiv2016

Effects of isovector scalar meson on hyperon star

We study the effects of isovector-scalar ($δ$)-meson on neutron star. Influence of $δ$-meson on both static and rotating neutron star is discussed. Inclusion of $δ$-meson in a neutron star system consisting of proton, neutron and electron, make the equation of state stiffer in higher density and consequently increases the maximum mass of the star. But induction of $δ$-meson in the hyperon star decreases the maximum mass of the hyperon star. This is due to the early evolution of hyperons in presence of $δ-$meson.

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arXiv2016

Modes of decay in neutron-rich nuclei

We calculate the ground, first intrinsic excited states and density distribution for neutron-rich thorium and uranium isotopes, within the framework of relativistic mean field(RMF) approach using axially deformed basis. The total nucleon densities are calculated, from which the cluster-structures inside the parent nuclei are determined. The possible modes of decay, like α-decay and \b{eta} -decay are analyzed. We find the neutron-rich isotopes are stable against α-decay, however they are very much unstable against \b{eta} -decay. The life time of these nuclei predicted to be tens of second against \b{eta} -decay.

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arXiv2015

Examining the stability of thermally fissile Th and U isotopes

The properties of recently predicted thermally fissile Th and U isotopes are studied within the framework of relativistic mean field (RMF) approach using axially deformed basis. We calculated the ground, first intrinsic excited state and matter density for highly neutron-rich thorium and uranium isotopes. The possible modes of decay like $α$-decay and $β$-decay are analyzed. We found that the neutron-rich isotopes are stable against $α$-decay, however they are very much unstable against $β$-decay. The life time of these nuclei predicted to be tens of second against $β$-decay. If these nuclei utilize before their decay time, a lots of energy can be produced within the help of multi-fragmentation fission. Also, these nuclei have a great implication in astrophysical point of view. The total nucleonic densities distribution are calculated, from which the clusters inside the parent nuclei are determined. %Most of the thorium isotopes are $α$ emitters, where as some %of them have short half-lives. In some cases, we found the isomeric states with energy range from 2 to 3 MeV and three minima in the potential energy surface of $^{228-230}$Th and $^{228-234}$U isotopes.

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arXiv2015

Effects of $NN$ potentials on $p$ nuclides in the A$\sim$100-120 region

Microscopic optical potentials for low energy proton reactions have been obtained by folding density dependent M3Y interaction derived from nuclear matter calculation with densities from mean field approach to study astrophysically important proton rich nuclei in mass 100-120 region. We compare S factors for low-energy $(p,γ)$ reactions with available experimental data and further calculate astrophysical reaction rates for $(p,γ)$ and $(p,n)$ reactions. Again we choose some nonlinear R3Y interactions from RMF calculation and folded them with corresponding RMF densities to reproduce experimental S factor values in this mass region. Finally the effect of nonlinearity on our result is discussed.

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