arXiv subjects

Mrutunjaya Bhuyan

Publications and source records attributed to Mrutunjaya Bhuyan.

5 recordsLinked to original sources

arXiv2025

Dark Matter Admixed White Dwarfs: A Single-Fluid Approach

In this study, we investigate the influence of an admixed fermionic dark matter (DM) component on the equilibrium structure of white dwarfs (WDs), with particular emphasis on the effects of varying the DM particle mass ($m_{\rm DM}$) and DM fraction ($f_{\rm DM}$). Notably, we employ a single-fluid approximation for the first time in this context, wherein the baryonic and DM contributions to the total energy density and pressure are treated within a unified framework, assuming non-interacting fermionic DM in hydrostatic equilibrium with baryons. We examine how variations in $m_{\mathrm{DM}}$ and $f_\mathrm{DM}$ modify the equation of state (EoS), the mass-radius relationship, and the internal mass and pressure distributions of WDs. Our results show that the presence of DM softens the EoS, with lighter DM particles providing stronger pressure support and leading to more extended stellar structures. Increasing the DM mass fraction leads to a more compact configuration, reducing both the radius and maximum mass of the WD. We further demonstrate that heavier DM particles enhance stellar compactness and can eventually drive the star toward gravitational instability. Moreover, the analysis of mass-radius relationships reveals that while small fractions of DM are consistent with observed WD masses, the radii predicted by our models are smaller than observations, suggesting additional influences such as rotation or magnetic fields. Our stability analysis confirms that the inclusion of dark matter does not lead to instability within the expected parameter space, indicating that white dwarfs admixed with dark matter can remain dynamically stable under certain conditions. These findings show that even a small admixture of DM can modify the structural properties and stability limits of WDs, providing a potential indirect astrophysical probe of DM particle properties.

astro-ph.SR↗

arXiv2022

Medium dependent relativistic NN potential: Application to the fusion dynamics

In-medium effects are introduced in the microscopic description of the effective nucleon-nucleon (NN) interaction potential entitled DDR3Y in terms of the density-dependent nucleon-meson couplings within the Relativistic-Hartree-Bogoliubov (RHB) approach. The nuclear densities of the interacting target and projectile nuclei and NN potentials are obtained for non-linear NL3$^*$ and TM1 parameter sets within the relativistic mean-field approach and density-dependent DDME1 and DDME2 parameter sets within the Relativistic-Hartree-Bogoliubov (RHB) formalism. The DDR3Y NN potential and the densities are used to obtain the nuclear potential by adopting the double folding approach. This nuclear potential is further used to probe the fusion dynamics within the $\ell-$summed Wong model for a few {\it even-even} systems leading to the formation of light, heavy and superheavy nuclei. The calculations are also performed for the relativistic R3Y, density-dependent and independent M3Y interaction potentials for the comparison. We observed that the DDR3Y NN potential gives a better overlap with the experimental data as compared to non-relativistic M3Y and DDM3Y NN potentials. From the comparison of R3Y and DDR3Y interactions, it is manifested that the inclusion of in-medium effects in terms of density-dependent nucleon-meson couplings raises the fusion barrier and consequently decreases the fusion and/or capture cross-section. Moreover, the nuclear densities, as well as the relativistic R3Y NN potential obtained for the NL3$^*$ parameter set, are observed to give a comparatively better fit to the experimental data.

nucl-th↗

arXiv2022

Systematic study of fusion barrier characteristics within the relativistic mean-field formalism

Background: The nuclear interaction potential and hence the fusion barrier formed between the interacting nuclei are the keys to understanding the complex fusion process dynamics. Purpose: This work intends to explore the fusion barrier characteristics of different target-projectile combinations within the relativistic mean-field (RMF) formalism. Methods: The density distributions of interacting nuclei and the microscopic R3Y NN interaction are obtained from relativistic mean-field (RMF) formalism for non-linear NL1, NL3, TM1, and relativistic-Hartree-Bogoliubov (RHB) approach for DDME2 parameter sets. The fusion and/or capture cross-section for the different reaction systems is calculated using the well-known $\ell$-summed Wong model. Results: The barrier height and position of 24 heavy-ion reaction systems are obtained for different nuclear density distributions and effective NN interaction potentials. The comparison of fusion and/or capture cross-section obtained from the $\ell$-summed Wong model is made with the available experimental data. Conclusions: The phenomenological M3Y NN potential is observed to give higher barrier heights than the relativistic R3Y NN potential for all the reaction systems. The comparison of results obtained from different relativistic parameter sets shows that the densities from NL1 and TM1 parameter sets give the lowest and highest barrier heights for all the systems under study. We observed higher barrier heights and lower cross-sections for DDR3Y NN potential as compared to density-independent R3Y NN potentials obtained for considered non-linear NL1, NL3 and TM1 parameter sets. According to the present analysis, it is concluded that the NL1 and NL3 parameter sets provide comparatively better overlap with the experimental fusion and/or capture cross-section than the TM1 and DDME2 parameter sets.

nucl-th↗

arXiv2019

Above-barrier heavy-ion fusion cross-sections using the relativistic mean-field approach: case of spherical colliding nuclei

The double folding (DF) approach is one of the widely used methods for finding nucleus-nucleus interaction potential. In the present work, the influence of the nuclear matter density on the DF potential and on the Coulomb barrier parameters is studied systematically for collisions of spherical nuclei. The value of the parameter $B_Z=Z_P Z_T/(A_P^{1/3}+A_T^{1/3})$ (estimating the Coulomb barrier height) varies in these calculations from 10 MeV up to 150 MeV. The novel feature of this study is that the nuclear densities came from the Relativistic Mean Field approach (RMF). For the nucleon-nucleon effective interaction, the M3Y forces with the finite range exchange term and density dependence are employed. The above barrier fusion cross sections are calculated within the framework of the trajectory model with surface friction. Results are compared with the previous study in which the nuclear density came from the Hartree-Fock (HF) calculations and with the high precision experimental data. This comparison demonstrates that i) agreement between the theoretical and experimental cross sections obtained with RMF and HF densities is of the same quality and ii) the values of the only adjustable parameter (friction strength) obtained with RMF and HF densities strongly correlate.

nucl-th↗

arXiv2019

Neutron star cooling and GW170817 constraint within quark-meson coupling models

In the present work we used five different versions of the quark-meson coupling (QMC) model to compute astrophysical quantities related to the GW170817 event and to neutron star cooling process. Two of the models are based on the original bag potential structure and three versions consider a harmonic oscillator potential to confine the quarks. The bag-like models also incorporate the pasta phase used to describe the inner crust of neutron stars. We show that the pasta phase always play a minor or negligible role in all studies. Moreover, while no clear correlation between the models that satisfy the GW170817 constraints and the slope of the symmetry energy is found, a clear correlation is observed between the slope and the fact that the cooling is fast or slow, i.e., fast (slow) cooling is related to higher (lower) values of the slope. We did not find one unique model that can describe, at the same time, GW170817 constraints and give a perfect description of the possible cooling processes.

astro-ph.HE↗