We present the evolution of the shell structure of nuclei in Hartree-Fock calculations using Skyrme's density-dependent effective nucleon-nucleon interaction. The role of the tensor part of the Skyrme interaction to the Hartree-Fock spin-orbit splitting in spherical spin unsaturated nuclei is reanalyzed. The contribution of a finite range tensor force to the spin-orbit splitting in closed shell nuclei is calculated. It is found that the exact matrix elements of a Gaussian and of a one-pion exchange tensor potential could be written as a product Skyrme's short range expression times a suppression factor which is almost constant for closed shell nuclei with mass number $A⩾48$. The suppression factor is $\sim 0.15$ for the one-pion exchange potential.

The azimuthal angle (ϕ) variation of the Coulomb and nuclear heavy ion (HI) potentials is studied in the framework of the double folding model, which is derived from realistic nuclear density distributions and a nucleon-nucleon ($\mathit{NN}$) interaction. The present calculation shows that the variation of HI potentials with the azimuthal angle depends strongly on the range of the $\mathit{NN}$ forces. For the long-range Coulomb force, the maximum variation with ϕ is about 0.9%, and for HI potential derived from zero-range $\mathit{NN}$ interaction the ϕ-variation can reach up to 90.0%. Our calculations are compared with the recent ϕ-dependence of the HI potential derived from proximity method. The present realistic ϕ-dependence calculations of the HI potential is completely different from the results of the proximity calculations.

The fade out of a collective enhancement of the nuclear level density is predicted (by an SU3 shell model) to give rise to a clear signature in the evolution of the spectral shape of evaporated charged particles with excitation energy. We have searched for this signature in the spectra of $\alpha$ particles emitted from ${}^{178}\mathrm{Hf}$ compound nuclei, with excitation energies between 54 and 124 MeV, formed in ${}^{18}\mathrm{O}+{}^{160}\mathrm{Gd}$ fusion reactions. The Gammasphere spectrometer provided us with the ability to construct channel-specific $\alpha$-particle spectra that could be compared to statistical-model calculations on a channel-by-channel basis. The expected clear signature of a rapid fade out of a collective enhancement was not found. The data are best reproduced by calculations that do not explicitly consider a collective enhancement and its fade out.

The electron positron annihilation reaction into four-pion production has been studied, through the channel $e^{+}+e^{-}\to \overline{\rho }+\rho$. The differential (and total) cross sections and various polarization observables for this reaction have been calculated in terms of the electromagnetic form factors of the corresponding ${\gamma }^{*}\rho \rho$ current. The elements of the spin-density matrix of the ρ meson were also calculated. Numerical estimations have been done, with the help of phenomenological form factors obtained in the spacelike region of the momentum transfer squared and analytically extended to the timelike region.

The presence of the long-range Coulomb force in dense stellar matter implies that the total charge cannot be associated with a chemical potential, even if it is a conserved quantity. As a consequence, the analytical properties of the partition sum are modified, changing the order of the phase transitions and affecting the possible occurrence of critical behaviors. The peculiar thermodynamic properties of this system can be understood introducing a model Hamiltonian where each charge is independently neutralized by a uniform background of opposite charge. Some consequences on the characteristics of mixed-phase structures in neutron star crusts and supernova cores are discussed.

An empirical rule, which is an extension of the rule for two-quasiparticle bands, is devised to check the favoured signature in three-quasiparticle bands of $A=153\text{−}187$ mass region. Its applications, for testing the favored signature, confirmation of the spin/parity assignments, and confirmation of the configuration assignments to three-quasiparticle bands, are discussed. Violation of the rule for tilted rotational bands supports the fact that signature does not remain a good quantum number for tilted bands.

The technique of recoil β tagging has been developed which allows prompt γ decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived β decay. This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in ${}^{78}\mathrm{Y}$ to be observed for the first time, as well as an extension in the knowledge of $T=1$ states in ${}^{74}\mathrm{Rb}$. From this new information it has been possible to compare Coulomb energy differences (CED) between $T=1$ states in ${}^{70}\mathrm{Br}$/${}^{70}\mathrm{Se}$, ${}^{74}\mathrm{Rb}$/${}^{74}\mathrm{Kr}$, and ${}^{78}\mathrm{Y}$/${}^{78}\mathrm{Sr}$. The $A=70$ CED exhibit an anomalous behavior which is inconsistent with all other known CED. This behavior may be accounted for qualitatively in terms of small variations in the Coulomb energy arising from shape changes.

The quasicontinuum of γ rays from the feeding and decay of superdeformed and normal bands in ${}^{152}\mathrm{Dy}$ have been extracted in one- and two-dimensional spectra. The $E_{\gamma }\text{−}{E}_{\gamma }$ correlations in the latter reveal strong ridges associated with superdeformed and normal states in this nucleus. The entry distributions for normal and superdeformed bands have been extracted from measured fold and sum-energy distributions. A Monte Carlo model was developed to simultaneously describe all the quasicontinuum and ridge spectra as well as the feeding intensity of the superdeformed bands. The rotational damping widths in the normal and superdeformed wells were derived based on a comparison of the data with model calculations of the continuum of γ rays at finite temperature.

A new channel of direct photon production from a quark-gluon plasma (QGP) is explored. This process appears at next-to-leading order in the presence of a charge asymmetry in the heated matter and may be effectively described as the bremsstrahlung of a real photon from a thermal gluon. The photon production from this new mechanism is calculated in the effective theory of QCD at high temperature. The results show that the photon production rate may not be as high as that of the annihilation and Compton scattering processes at low baryon density, but could become important in baryon-rich matter.

An application of the new formulation of the eigenchannel method [R. Szmytkowski, Ann. Phys. (N.Y.) 311, 503 (2004)] to quantum scattering of Dirac particles from nonlocal separable potentials is presented. Eigenchannel vectors, related directly to eigenchannels, are defined as eigenvectors of a certain weighted eigenvalue problem. Moreover, negative cotangents of eigenphase-shifts are introduced as eigenvalues of that spectral problem. Eigenchannel spinor as well as bispinor harmonics are expressed throughout the eigenchannel vectors. Finally, the expressions for the bispinor as well as matrix scattering amplitudes and total cross section are derived in terms of eigenchannels and eigenphase-shifts. An illustrative example is also provided.

Covariant density functional theory, which has so far been applied only within the framework of static and time-dependent mean-field theory, is extended to include particle-vibration coupling (PVC) in a consistent way. Starting from a conventional energy functional, we calculate the low-lying collective vibrations in the relativistic random phase approximation (RRPA) and construct an energy-dependent self-energy for the Dyson equation. The resulting Bethe-Salpeter equation in the particle-hole (p-h) channel is solved in the time blocking approximation (TBA). No additional parameters are used, and double counting is avoided by a proper subtraction method. The same energy functional, i.e., the same set of coupling constants, generates the Dirac-Hartree single-particle spectrum, the static part of the residual p-h interaction, and the particle-phonon coupling vertices. Therefore, a fully consistent description of nuclear excited states is developed. This method is applied for an investigation of damping phenomena in the spherical nuclei with closed shells ${}^{208}\mathrm{Pb}$ and ${}^{132}\mathrm{Sn}$. Since the phonon coupling terms enrich the RRPA spectrum with a multitude of p-h⊗phonon components, a noticeable fragmentation of the giant resonances is found, which is in full agreement with experimental data and with results of the semiphenomenological nonrelativistic approach.

Working within the framework of the Coulomb modified Glauber model we fit the elastic differential scattering cross section of 240 MeV $\alpha$ particle on ${}^{58}\mathrm{Ni}$ using the effective $N\text{−}\alpha$ amplitude with one adjustable parameter. It is found that once the effective amplitude is calibrated on ${}^{58}\mathrm{Ni}$ by varying the adjustable parameter, it very nicely reproduces the available elastic $\alpha$ scattering data on other nuclei at the same energy.

We present a hybrid equation of state (EoS) for dense matter in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark matter phase is modelled according to a recently developed covariant, nonlocal chiral quark model. We show that modern observational constraints for compact star masses ($M~2M_{\odot }$) can be satisfied when a small vector-like four quark interaction is taken into account. The corresponding isospin symmetric EoS is consistent with flow data analyses of heavy ion collisions and points to a deconfinement transition at about 0.55 fm${}^{-3}$.

The similarity renormalization group (SRG) is based on unitary transformations that suppress off-diagonal matrix elements, forcing the Hamiltonian toward a band-diagonal form. A simple SRG transformation applied to nucleon-nucleon interactions leads to greatly improved convergence properties while preserving observables and provides a method to consistently evolve many-body potentials and other operators.

We calculate parity-dependent level densities for the even-even isotopes ${}^{58,62,66}\mathrm{Fe}$ and ${}^{58}\mathrm{Ni}$ and the odd-$A$ nuclei ${}^{59}\mathrm{Ni}$ and ${}^{65}\mathrm{Fe}$ using the shell model Monte Carlo method. We perform these calculations in the complete $\mathit{fp}\text{−}\mathit{gds}$ shell-model space using a pairing+quadrupole residual interaction. We find that, due to pairing of identical nucleons, the low-energy spectrum is dominated by positive parity states. Although these pairs break at around the same excitation energy in all nuclei, the energy dependence of the ratio of negative-to-positive parity level densities depends strongly on the particular nucleus of interest. We find equilibration of both parities at noticeably lower excitation energies for the odd-$A$ nuclei ${}^{59}\mathrm{Ni}$ and ${}^{65}\mathrm{Fe}$ than for the neighboring even-even nuclei ${}^{58}\mathrm{Ni}$ and ${}^{66}\mathrm{Fe}$.

The collisional energy gain of a heavy quark due to chromoelectromagnetic field fluctuations in a quark-gluon plasma is investigated. The field fluctuations lead to an energy gain of the quark for all velocities. The net effect is a reduction of the collisional energy loss by 15–40% for parameters relevant at RHIC energies.

Solar neutrino fluxes depend both on astrophysical and on nuclear physics inputs, namely on the cross sections of the reactions responsible for neutrino production inside the Solar core. While the flux of solar ${}^8\mathrm{B}$ neutrinos has been recently measured at Superkamiokande with a 3.5% uncertainty and a precise measurement of ${}^7\mathrm{Be}$ neutrino flux is foreseen in the next future, the predicted fluxes are still affected by larger errors. The largest nuclear physics uncertainty to determine the fluxes of ${}^8\mathrm{B}$ and ${}^7\mathrm{Be}$ neutrinos comes from the ${}^3\mathrm{He}$($\alpha ,\gamma$)${}^7\mathrm{Be}$ reaction. The uncertainty on its S-factor is due to an average discrepancy in results obtained using two different experimental approaches: the detection of the delayed γ rays from ${}^7\mathrm{Be}$ decay and the measurement of the prompt γ emission. Here we report on a new high precision experiment performed with both techniques at the same time. Thanks to the low background conditions of the Gran Sasso LUNA accelerator facility, the cross section has been measured at $E_{\mathrm{c}.\mathrm{m}.}=170$, 106, and 93 keV, the latter being the lowest interaction energy ever reached. The S-factors from the two methods do not show any discrepancy within the experimental errors. An extrapolated $S(0)=0.560\pm 0.017$ keV barn is obtained. Moreover, branching ratios between the two prompt γ-transitions have been measured with 5–8% accuracy.

The lifetime of the first excited state of ${}^{201}\mathrm{Hg}$, populated by the ${}^{201}\mathrm{Tl}$ electron capture decay and subsequent $\gamma$-ray transitions, has been measured for the first time. This measurement has been carried out using a coincidence between an internal conversion electron and a γ-ray. The half-life of 81±5 ns has been obtained and $B(E2)$ and $B(M1)$ values were deduced and compared to previous estimates. With these reduced matrix elements, the excitation rate of the first excited state of ${}^{201}\mathrm{Hg}$ in plasma have been calculated in the frame of a Nuclear excitation by electronic transition (NEET) process.

To study the dynamics of heavy ion fusion reactions in the lower mass region, experiments were carried out to measure the cross sections of radioactive residues produced in the interaction of the ${}^{16}\mathrm{O}$ ion with ${}^{27}\mathrm{Al}$ target nucleus at 19 different energies in very close intervals covering the energy range from $\approx 58$ to 94 MeV, using the well-known recoil catcher off-line γ-ray spectroscopy technique. The simulation of experimental data was performed using statistical-model-based computer codes, viz., CASCADE, PACE2, and ALICE-91. The analysis of measured excitation functions indicates that these residues are likely to be produced by complete fusion, incomplete fusion, and direct reaction processes. Furthermore, to confirm the contribution of different reaction channels, a complementary experiment was performed that measured the angular distributions of the residues produced in the ${}^{16}\mathrm{O}+{}^{27}\mathrm{Al}$ system at 85 MeV beam energy. The analysis of the results of both experiments indicates that at these energies, the direct reactions compete with complete fusion and incomplete fusion reaction processes.