abstract

The generalized Brink–Axel (gBA) hypothesis suggests that the \(\gamma \)-ray strength function (\(\gamma \)SF) of a nucleus only depends on the \(\gamma \)-ray energy, and not on the properties of the initial and final excitation energy levels between which the nucleus decays. This hypothesis has been tested in various studies and it is still controversial. In this study, the gBA hypothesis was tested in the \(A=138\) nuclear mass region by rigorously investigating the dependence of the \(\gamma \)SF of \(^{138}\)La on both initial and final excitation energies. The results showed that the shape and absolute value of the \(\gamma \)SF are independent of the initial and final excitation energy. Therefore, the results of this work are in support of the generalized Brink–Axel hypothesis.

abstract

Inelastic scattering of charged hadronic systems is studied by considering a new approximation scheme to effective potential. A short-ranged electromagnetic interaction with the same range as the nuclear one is adapted to visualize the effect of such a potential model in treating the off-energy-shell scattering of the nuclear systems. Under this approximation, the Schrödinger equation admits an exact analytical solution and the related off-shell quantities are expressed in their maximal reduced form to make them amenable to numerical treatment. The nucleon–light nuclei system is studied and close agreement in numerical results with other works is found.

abstract

The beta-decay rates of neutron-rich nuclei far from the stability are still very limited due to the lack of experimental data. In this paper, we calculated the half-lives of the exotic nuclei close to the neutron drip line by using a recent semi-empirical formula (\(F_{\mathrm {Zh}}\)). The \(\beta \)-decay \(Q\)-values calculated using the finite-range droplet macroscopic (FRDM) model and taken from the AME2020 database (with and without uncertainty) were used in the calculations to investigate the impact of the mass uncertainty on the half-life predictions. We found that a deviation of 7% in the \(Q\)-value can lead to an uncertainty of 40% in the half-life and a large change, up to two orders of magnitude, in the r-process abundance. The approach combining the AME2020 \(Q\)-value and \(F_{\mathrm {Zh}}\) model has emerged as a good tool for the half-life prediction. The estimated half-lives are necessary for the precise mass measurements and r-process simulations.

abstract

We consider the quantum kinetic-theory description for interacting massive spin-half fermions using the Wigner function formalism. We derive a general kinetic theory description assuming that the spin effects appear at the classical and quantum level. To track the effect of such different contributions, we use the semi-classical expansion method to obtain the generalized dynamical equations including spin, analogous to the classical Boltzmann equation. This approach can be used to obtain a collision kernel involving local as well as non-local collisions among the microscopic constituent of the system and eventually, a framework of spin hydrodynamics ensuring the conservation of the energy-momentum tensor and total angular momentum tensor.