We introduce a new relativistic energy density functional constrained by the ground state properties of atomic nuclei along with the isoscalar giant monopole resonance energy and dipole polarizability in 208 Pb. A unified framework of the relativistic Hartree-Bogoliubov model and random phase approximation based on the relativistic density-dependent point coupling interaction is established in order to determine the DD-PCX parameterization by χ 2 minimization. This procedure is supplemented with the co-variance analysis in order to estimate statistical uncertainties in the model parameters and observables. The effective interaction DD-PCX accurately describes the nuclear ground state properties including the neutron-skin thickness, as well as the isoscalar giant monopole resonance excitation energies and dipole polarizabilities. The implementation of the experimental data on nuclear excitations allows constraining the symmetry energy close to the saturation density, and the incompressibility of nuclear matter by using genuine observables on finite nuclei in the χ 2 minimization protocol, rather than using pseudo-observables on the nuclear matter, or by relying on the ground state properties only, as it has been customary in the previous studies.Solving the quantum many-body problem of strongly interacting nucleons represents one of the fundamental challenges not only for understanding the phenomena of nuclear structure and dynamics, but also for various applications of astrophysical relevance, e.g., modeling the stellar evolution, supernova explosion, the properties of compact stars, the synthesis of chemical elements in the universe, etc. Among a variety of theoretical frameworks to address this problem, the nuclear energy density functional (EDF) represents a unified approach to study quantitatively static and dynamic properties of finite nuclei along the nuclide map [1,2] as well as the equation of state of nuclear matter [3]. A considerable progress has been achieved in constructing and optimizing the phenomenological EDFs, both in non-relativistic [4-6] and relativistic [1,[7][8][9]11] frameworks. Recently, the construction of the EDFs was also inspired by ab initio calculations [12] and effective field theories [13]. As pointed out in Ref. [14], strengths of the tensor forces guided by ab initio relativistic Brueckner-Hartree-Fock calculations can also be used as a guide for the future ab initio derivations of the EDFs. At present, only the phenomenological EDFs provide a level of accuracy required to quantitatively describe the nuclear properties across the whole nuclide map.So far, the EDFs have mainly been parametrized with the experimental data on the ground state properties of nuclei. These observables alone are often not enough to constrain the effective interaction completely, especially its isovector channel, thus the protocols to determine the EDF's parameters often included constraints on the pseudo-observables on the nuclear matter properties. The neutron skin thickness r np , isovector dipole ex...

The effect of temperature on the evolution of the isovector dipole and isoscalar quadrupole excitations in 68 Ni and 120 Sn nuclei is studied within the fully self-consistent finite temperature quasiparticle random phase approximation framework, based on the Skyrme-type SLy5 energy density functional. The new low-energy excitations emerge due to the transitions from thermally occupied states to the discretized continuum at finite temperatures, whereas the isovector giant dipole resonance is not strongly impacted by the increase of temperature. The radiative dipole strength at low energies is also investigated for the 122 Sn nucleus, becoming compatible with the available experimental data when the temperature is included. In addition, both the isoscalar giant quadrupole resonance and low-energy quadrupole states are sensitive to the temperature effect: while the centroid energies decrease in the case of the isoscalar giant quadrupole resonance, the collectivity of the first 2 + state is quenched and the opening of new excitation channels fragments the low-energy strength at finite temperatures.

The relativistic and non-relativistic finite temperature proton-neutron quasiparticle random phase approximation (FT-PNQRPA) methods are developed to study the interplay of the pairing and temperature effects on the Gamow-Teller excitations in open-shell nuclei, as well as to explore the model dependence of the results by using two rather different frameworks for effective nuclear interactions. The Skyrme-type functional SkM* is employed in the non-relativistic framework, while the densitydependent meson-exchange interaction DD-ME2 is implemented in the relativistic approach. Both the isoscalar and isovector pairing interactions are taken into account within the FT-PNQRPA. Model calculations show that below the critical temperatures the Gamow-Teller excitations display a sensitivity both to the finite temperature and pairing effects, and this demonstrates the necessity for implementing both in the theoretical framework. The established FT-PNQRPA opens perspectives for the future complete and consistent description of astrophysically relevant weak interaction processes in nuclei at finite temperature such as beta decays, electron capture and neutrino-nucleus reactions.

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We study the finite temperature Hartree-Fock-BCS approximation for selected stable Sn nuclei with zero-range Skyrme forces. Hartree Fock BCS approximation allows for a straightforward interpretation of the results since it involves u and v's which are not matrices as in HFB. Pairing transitions from superfluid to the normal state are studied with respect to the temperature. The temperature dependence of the nuclear radii and neutron skin are also analyzed. An increase of proton and neutron radii is obtained in neutron rich nuclei especially above the critical temperature. Using different Skyrme energy functionals, it is found that the correlation between the effective mass in symmetric nuclear matter and the critical temperature depends on the pairing prescription. The temperature dependence of the nucleon effective mass is also investigated, showing that proton and neutron effective masses display different behavior below and above the critical temperature, due to the small temperature dependence of the density.

The electron-capture process plays an important role in the evolution of the core collapse of a massive star that precedes the supernova explosion. In this study, the electron capture on nuclei in stellar environment is described in the relativistic energy density functional framework, including both the finite-temperature and nuclear pairing effects. Relevant nuclear transitions J π = 0 ± , 1 ± , 2 ± are calculated using the finite-temperature proton-neutron quasiparticle random-phase approximation with the density-dependent meson-exchange effective interaction DD-ME2. The pairing and temperature effects are investigated in the Gamow-Teller transition strength as well as the electron-capture cross sections and rates for 44 Ti and 56 Fe in the stellar environment. It is found that the pairing correlations establish an additional unblocking mechanism similar to the finite-temperature effects, that can allow otherwise blocked single-particle transitions. Inclusion of pairing correlations at finite temperature can significantly alter the electron-capture cross sections, even up to a factor of 2 for 44 Ti, while for the same nucleus electron-capture rates can increase by more than one order of magnitude. We conclude that for the complete description of electron capture on nuclei both pairing and temperature effects must be taken into account.

The magic nature of the 54 Ca nucleus is investigated in the light of the recent experimental results. We employ both HFB and HF+BCS methods using Skyrme-type SLy5, SLy5+T and T44 interactions. The evolution of the single-particle spectra is studied for the N=34 isotones: 60 Fe, 58 Cr, 56 Ti and 54 Ca. An increase is obtained in the neutron spinorbit splittings of p and f states due to the effect of the tensor force which also makes 54 Ca a magic nucleus candidate. QRPA calculations on top of HF+BCS are performed to investigate the first J π =2 + states of the calcium isotopic chain. A good agreement for excitation energies is obtained when we include the tensor force in the mean-field part of the calculations. The first 2 + states indicate a subshell closure for both 52 Ca and 54 Ca nuclei. We confirm that the tensor part of the interaction is quite essential in explaining the neutron subshell closure in 52 Ca and 54 Ca nuclei.

In recent years, artificial neural networks and their applications for large data sets have become a crucial part of scientific research. In this work, we implement the Multilayer Perceptron (MLP), which is a class of feedforward artificial neural network (ANN), to predict ground-state binding energies of atomic nuclei. Two different MLP architectures with three and four hidden layers are used to study their effects on the predictions. To train the MLP architectures, two different inputs are used along with the latest atomic mass table and changes in binding energy predictions are also analyzed in terms of the changes in the input channel. It is seen that using appropriate MLP architectures and putting more physical information in the input channels, MLP can make fast and reliable predictions for binding energies of atomic nuclei, which is also comparable to the microscopic energy density functionals.