Density Dependent M3Y Effective Interaction Research Articles

Gravitational waves from non-radial perturbations in neutron stars

In the present work, we explore the Rossby mode perturbations in case of neutron stars as sources of continuous gravitational waves. The intensity and time evolution of the emitted gravitational waves in terms of the amplitude of the strain tensor are estimated in the slow rotation approximation using β-equilibrated neutron star matter obtained from density dependent M3Y effective interaction. For a wide range of neutron star masses, the fiducial gravitational and various viscous time scales, the critical frequencies and the time evolutions of the frequencies are calculated. Unlike other non-radial perturbations, amplitude of Rossby mode perturbation increases due to the emission of gravitational waves which carry angular momentum of the star to infinity. Hence, existence of such perturbation in a star implies a positive rate of change in the angular momentum transfer. It, therefore, implies that for a particular neutron star, the intensity of gravitational wave emission increases with time until the angular frequency reduces down to a critical value below which the star stops emitting radiation.

Gravitational waves from isolated neutron stars: Mass dependence of r -mode instability

In this work we study the r-mode instability windows and the gravitational wave signatures of neutron stars in the slow rotation approximation using the equation of state obtained from the density dependent M3Y effective interaction. We consider the neutron star matter to be $\beta$-equilibrated neutron-proton-electron matter at the core with a rigid crust. The fiducial gravitational and viscous timescales, the critical frequencies and the time evolutions of the frequencies and the rates of frequency change are calculated for a range of neutron star masses. We show that the young and hot rotating neutron stars lie in the r-mode instability region. We also emphasize that if the dominant dissipative mechanism of the r-mode is the shear viscosity along the boundary layer of the crust-core interface, then the neutron stars with low $L$ value lie in the r-mode instability region and hence emit gravitational radiation.

Nuclear constraints on the core-crust transition and crustal fraction of moment of inertia of neutron stars

The crustal fraction of moment of inertia in neutron stars is calculated using $\beta$-equilibrated nuclear matter obtained from density dependent M3Y effective interaction. The transition density, pressure and proton fraction at the inner edge separating the liquid core from the solid crust of the neutron stars determined from the thermodynamic stability conditions are found to be $\rho_t=$ 0.0938 fm$^{-3}$, P$_t=$ 0.5006 MeV fm$^{-3}$ and $x_{p(t)}=$ 0.0308, respectively. The crustal fraction of the moment of inertia can be extracted from studying pulsar glitches and is most sensitive to the pressure as well as density at the transition from the crust to the core. These results for pressure and density at core-crust transition together with the observed minimum crustal fraction of the total moment of inertia provide a new limit for the radius of the Vela pulsar: $R \geq 4.10 + 3.36 M/M_\odot$ kms.

Study of resonance states of 11Be with isospectral bound state microscopic potential

The theoretical procedure of supersymmetric quantum mechanics (SQM) is adopted for the first time to study quasi-bound states of a weakly bound nuclear system using microscopic potential. The density dependent M3Y (DDM3Y) effective interaction was found earlier to give a satisfactory description of radioactivity, nuclear matter and scattering. In the present work, we have microscopically generated a two-body potential in a single folding model using the DDM3Y effective interaction. From this potential, SQM generated a family of isospectral potentials for 11Be (10Be + n). We investigated the 5/2+, 3/2− and 3/2+ resonance states of 11Be. The experimental data and the present calculations of excitation energies of the above resonance states are found to be in good agreement.

Effective interaction: From nuclear reactions to neutron stars

An equation of state (EoS) for symmetric nuclear matter is constructed using the density dependent M3Y effective interaction and extended for isospin asymmetric nuclear matter. Theoretically obtained values of symmetric nuclear matter incompressibility, isobaric incompressibility, symmetry energy and its slope agree well with experimentally extracted values. Folded microscopic potentials using this effective interaction, whose density dependence is determined from nuclear matter calculations, provide excellent descriptions for proton, alpha and cluster radioactivities, elastic and inelastic scattering. The nuclear deformation parameters extracted from inelastic scattering of protons agree well with other available results. The high density behavior of symmetric and asymmetric nuclear matter satisfies the constraints from the observed flow data of heavy-ion collisions. The neutron star properties studied using $\beta$-equilibrated neutron star matter obtained from this effective interaction reconcile with the recent observations of the massive compact stars.

From nuclear reactions to compact stars: A unified approach

An equation of state (EoS) for symmetric nuclear matter is constructed using the density dependent M3Y effective interaction and extended for isospin asymmetric nuclear matter. Theoretically obtained values of symmetric nuclear matter incompressibility, isobaric incompressibility, symmetry energy and its slope agree well with experimentally extracted values. Folded microscopic potentials using this effective interaction, whose density dependence is determined from nuclear matter calculations, provide excellent descriptions for proton, alpha and cluster radioactivities, elastic and inelastic scattering. The nuclear deformation parameters extracted from inelastic scattering of protons agree well with other available results. The high density behavior of symmetric and asymmetric nuclear matter satisfies the constraints from the observed flow data of heavy-ion collisions. The neutron star properties studied using $\beta$-equilibrated neutron star matter obtained from this effective interaction for pure hadronic model agree with the recent observations of the massive compact stars such as PSR J1614-2230, but if a phase transition to quark matter is considered such agreement is no longer possible.

Cluster radioactivity in very heavy nuclei: a new perspective

Exotic cluster decay of very heavy nuclei is studied using the microscopic nuclear potentials obtained by folding density dependent M3Y effective interaction with the densities of the cluster and the daughter nuclei. The microscopic nuclear potential, Coulomb interaction and the centrifugal barrier arising out of spin-parity conservation are used to obtain the potential between the cluster and the daughter nuclei. Half life values are calculated in the WKB framework and the preformation factors are extracted. The latter values are seen to have only a very weak dependence on the mass of the emitted cluster.

Nuclear symmetry energy from effective interaction and masses of isospin asymmetric nuclei

Binding energy of isospin asymmetric nuclei can be accessed with minimally modified formula along the lines of the liquid droplet model by partitioning the symmetry term into volume and surface terms. The volume symmetry energy coefficient extracted from finite nuclei provides a constraint on the nuclear symmetry energy. This approach also yields the neutron skin of a finite nucleus through its relationship with the volume and surface symmetry terms and the Coulomb energy coefficient. The symmetry energy at saturation density obtained from the isoscalar as well as isovector components of the density dependent M3Y effective interaction is found to be in close agreement with the volume symmetry energy coefficient extracted from the measured atomic masses.

α decay half-lives of new superheavy nuclei within a generalized liquid drop model

The \ensuremath{\alpha} decay half-lives of the recently produced isotopes of the 112, 114, 116 and 118 nuclei and decay products have been calculated in the quasi-molecular shape path using the experimental ${Q}_{\ensuremath{\alpha}}$ value and a Generalized Liquid Drop Model including the proximity effects between nucleons in the neck or the gap between the nascent fragments. Reasonable estimates are obtained for the observed \ensuremath{\alpha} decay half-lives. The results are compared with calculations using the Density-Dependent M3Y effective interaction and the Viola-Seaborg-Sobiczewski formulae. Generalized Liquid Drop Model predictions are provided for the \ensuremath{\alpha} decay half-lives of other superheavy nuclei using the Finite Range Droplet Model ${Q}_{\ensuremath{\alpha}}$ and compared with the values derived from the VSS formulae.