A simple model of a relativistic optical model is constructed by reducing the three-body Bethe-Salpeter equation to an effective two-body optical model. A corresponding effective current is derived for use with the optical-model wave functions. It is shown that this current satisfies a Ward-Takahashi identity involving the optical potential resulting in conserved current matrix elements.

The inelastic, two-neutron and α transfer and quasielastic cross sections for the ${}^{18}\mathrm{O}+{}^{110}\mathrm{Pd}$ system have been measured in the near barrier region (40 MeV $⩽E_{\mathrm{lab}}⩽58$ MeV). The experiments were performed in the São Paulo Pelletron laboratory. Coupled-channel analysis of the experimental data was performed using the São Paulo potential as a microscopic bare interaction. In the calculations, low-lying inelastic excitations, one- and two-neutron and α transfers to the target were considered as the main couplings, with no extra surface absorption. The agreement between the theoretical results and the experimental data is good. The role played by the coupled channels is very different in comparison with similar data analyses for the closed-shell region around ${}^{58}\mathrm{Ni}$.

A systematic investigation of the average multiplicities of light charged particles and intermediate mass fragments emitted in peripheral and semiperipheral collisions is presented as a function of the beam energy, violence of the collision, and mass of the system. The data have been collected with the FIASCO setup in the reactions ${}^{93}\mathrm{Nb}+{}^{93}\mathrm{Nb}$ at $(17,23,30,38)A$ MeV and ${}^{116}\mathrm{Sn}+{}^{116}\mathrm{Sn}$ at $(30,38)A$ MeV. The midvelocity emission has been separated from the emission of the projectile-like fragment. This last component appears to be compatible with an evaporation from an equilibrated source at normal density, as described by the statistical code GEMINI at the appropriate excitation energy. On the contrary, the midvelocity emission presents remarkable differences in both the dependence of the multiplicities on the energy deposited in the midvelocity region and the isotopic composition of the emitted light charged particles.

It is shown that the experimentally observed decrease of nuclear symmetry energy with increasing centrality or excitation energy in isotopic scaling analyses of heavy-ion reactions can be well understood analytically within a degenerate Fermi gas model. The evolution of the symmetry energy is found to be mainly due to the variation in the freeze-out density rather than temperature. The isoscaling analyses are useful for probing the interaction part of the nuclear symmetry energy, provided that both the freeze-out temperature and density of the fragments can be inferred simultaneously from the experiments.

One of the most striking features in neutron-rich nuclei is the disappearance of magic number $N=8$ or 20, which indicates a change of single-particle energy spectra and the disappearance of a large energy gap at the magic number. A sum-rule method is formulated, based on the shell model, for the evaluation of single-particle energies. It is shown that the triplet-even central component of the $\mathit{NN}$ interaction plays a decisive role through the monopole interaction for a change of single-particle energy spectra, leading to a rapid decrease of the energy gap at $N=8$ and 20. The triplet-even attraction is due partly to the original central interaction and partly to the second-order tensor correlations of the one-pion exchange potential. A multipole expansion analysis of $\mathit{NN}$ interactions shows that the contribution to the single-particle energy from the monopole interactions between two orbits depends on the nodal quantum numbers of the orbits.

A microcanonical multifragmentation model (MMM) is used for investigating whether equilibration really occurs in the dynamical evolution of two heavy ion collisions simulated via a stochastic mean field approach. The standard deviation function between the dynamically obtained freeze-out fragment distributions corresponding to the reaction ${}^{129}\mathrm{Xe}+{}^{119}\mathrm{Sn}$ at 32 MeV/nucleon and the MMM ones corresponding to a wide range of mass, excitation energy, freeze-out volume, and nuclear level density cutoff parameter shows a unique minimum. A distinct statistically equilibrated stage is identified in the dynamical evolution of the system.

Total cross sections for proton induced fission of ${}^{\mathrm{nat}}\mathrm{Pb}$, ${}^{209}\mathrm{Bi}$, ${}^{232}\mathrm{Th}$, ${}^{233}\mathrm{U}$, ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, ${}^{237}\mathrm{Np}$, and ${}^{239}\mathrm{Pu}$ nuclei were measured in the range 200–1000 MeV with an energy step of 100 MeV. The experiment was carried out at 1 GeV in a PNPI synchrocyclotron. Complementary fragments of the binary fission from a thin target were detected in coincidence by two parallel plate avalanche counters (PPAC) located close to the target. An assembly of the two PPACs and with the target in between them was placed directly into the beam, which provided a large solid angle acceptance. The beam monitoring system employed a scintillation counter telescope that was used for direct proton counting as well as for registration of the elastic $\mathit{pp}$-scattering events from the auxiliary (${\mathrm{CH}}_2){}_n$ target. The measured energy dependence of the total fission cross sections is presented. The results are compared with other available experimental data as well as with calculations in the frame of the cascade-evaporation model.

We analyze thermonuclear and pycnonuclear fusion reactions in dense matter containing atomic nuclei of different types. We extend a phenomenological expression for the reaction rate, proposed recently by Gasques et al. [Phys. Rev. C 72, 025806 (2005)] for the one-component plasma of nuclei, to the multicomponent plasma. The expression contains several fit parameters which we adjust to reproduce the best microscopic calculations available in the literature. Furthermore, we show that pycnonuclear burning is drastically affected by an (unknown) structure of the multicomponent matter (a regular lattice, a uniform mix, etc.). We apply the results to study nuclear burning in a ${}^{12}C{\text{−}}^{16}O$ mixture. In this context, we present new calculations of the astrophysical $S$ factors for carbon-oxygen and oxygen-oxygen fusion reactions. We show that the presence of a C-O lattice can strongly suppress carbon ignition in white dwarf cores and neutron star crusts at densities $\rho \gtrsim 3\times {10}^9$ g cm${}^{-3}$ and temperatures $T\lesssim {10}^8$ K.

Macroscopic-microscopic calculations have been performed with the Yukawa folded mean field for 134 spherical even-even nuclei and 6 deformed ones at temperatures $0⩽T⩽5$ MeV and elongations ranging from oblate shapes to the scission configuration of fissioning nuclei. The Strutinsky type free-energy shell corrections for this sample of nuclei and their temperature and deformation dependence are found by a folding procedure in particle-number space. The average dependence of the single-particle level-density parameter on mass number $A$ and isospin $I$ is determined and compared with previous estimates obtained using the relativistic mean-field theory, the Hartree-Fock approximation with the Skyrme effective interaction, and the phenomenological Thomas-Fermi approach adjusted to experimental data. The estimates for the level-density parameter obtained for different deformations are fitted by a liquid-drop type expression.

I find that data for the reaction ${}^{10}\mathrm{Be}$$(p,\gamma )$ can be reasonably well described with a $1/2^{+}$ resonance whose width is 640 keV, rather than the accepted 210 keV.

The nuclear $g$-factors of the one-quasiparticle isomeric state ${\frac{9}{2}}^{-}$ at 165.8 keV and the three-quasiparticle isomeric state ${\frac{21}{2}}^{-}$ at 1713.2 keV in ${}^{173}\mathrm{Ta}$ nuclei have been measured using the time differential perturbed angular distribution technique. The nuclear reaction ${}^{165}\mathrm{Ho}$(${}^{12}\mathrm{C}$, $4n$γ)${}^{173}\mathrm{Ta}$ was used to populate these isomeric states, and the recoiling ${}^{173}\mathrm{Ta}$ nuclei were implanted into a thick tantalum backing in the presence of a 7.04(4) kG external magnetic field. The measured value $g$(${\frac{9}{2}}^{-}$) = +0.591(18) shows that the ${\frac{9}{2}}^{-}$ isomeric state is not a pure single-particle state but may have a collective contribution due to the octupole excitation of the core. Based on the measured value $g$(${\frac{21}{2}}^{-}$) = + 0.620(15) and multi-quasiparticle calculations, the ${\frac{21}{2}}^{-}$ isomeric state is assigned a mixed configuration: ${\pi }^3${${\frac{9}{2}}^{-}$[514], ${\frac{7}{2}}^{+}$[404], ${\frac{5}{2}}^{+}$[402]} (39%) and ${\pi }^1${${\frac{7}{2}}^{+}$[404]}$\otimes$ ${\nu }^2${${\frac{7}{2}}^{-}$[514], ${\frac{7}{2}}^{+}$[633]} (61%).

We present a relativistic model for computing the neutrino mean free path in neutron matter. In this model, neutron matter is described as a noninteracting Fermi gas in β equilibrium. We present results for the neutrino mean free path for temperatures of 0 to 50 MeV and a broad range of neutrino energies. We show that relativistic effects cause a considerable enhancement of neutrino-scattering cross sections in neutron matter. The influence of the $Q^2$ dependence in the electroweak form factors and the inclusion of a weak-magnetic term in the hadron current is discussed. The weak-magnetic term in the hadron current is at the origin of some selective spin dependence for the nucleons that are subject to neutrino interactions.

Very recent inelastic α-scattering data on the isoscalar monopole and dipole strength distributions in ${}^{56}\mathrm{Fe}$, ${}^{58}\mathrm{Ni}$, and ${}^{60}\mathrm{Ni}$ are analyzed in the relativistic quasiparticle random-phase approximation (RQRPA) with the DD-ME2 effective nuclear interaction (nuclear matter compression modulus ${\mathrm{K}}_{\mathrm{nm}}=251$ MeV). The calculation nicely reproduces the observed asymmetric shapes of the monopole strength, and the bimodal structure of the dipole strength distributions. The RQRPA centroid and mean energies are in very good qualitative agreement with the experimental values both for the monopole, and for the low- and high-energy components of the dipole transition strengths. It is noted, however, that while DD-ME2 reproduces in detail the excitation energies of the giant monopole resonances (GMR) in nuclei with $A⩾90$, the theoretical centroids are systematically above the experimental values in lighter nuclei with $A⩽60$. The latter can be reproduced with an effective interaction with a lower value of ${\mathrm{K}}_{\mathrm{nm}}\approx 230$ MeV but, because of the asymmetric shapes and pronounced fragmentation of the monopole strength distributions, isoscalar GMR data in light nuclei cannot provide accurate estimates of the nuclear matter compression modulus.

The self-consistent random-phase approximation (SCRPA) is extended to nonzero temperature. Within the SCRPA, the collective dynamics of nucleon pairs is built on the occupation numbers that deviate from the Fermi-Dirac distribution as a result of temperature-dependent correlations beyond the RPA. The equations for single-particle occupation numbers are derived using the method of the double-time Green's functions. The approach is applied to the Richardson model of pairing. The results of numerical calculations for energies of states and occupation numbers, as well as for the thermodynamic quantities such as the excitation energy and heat capacity of the system, are compared with those obtained within the conventional RPA and the perturbative thermal SCRPA and with the exact results. We find that, overall, the SCRPA offers a better agreement with the exact results.

The $J$-matrix inverse scattering nucleon-nucleon potentials (JISP), describing both two-nucleon data and bound and resonant states of light nuclei to high accuracy, are tested on the total photoabsorption cross sections of ${}^2\mathrm{H}$, ${}^3\mathrm{H}$, and ${}^{3,4}\mathrm{He}$. The calculations in the three- and four-body systems are carried out via the Lorentz integral transform method and the hyperspherical harmonics (HH) technique. To this end the HH formalism has been adapted to accommodate nonlocal potentials. The cross sections calculated with the JISP are compared to those obtained with more traditional realistic interactions, which include two- and three-nucleon forces. Although the results of the two kinds of potential models do not differ significantly at lower energies, beyond the resonance peak they show fairly large discrepancies, which increase with the nuclear mass. We argue that these discrepancies may be due to a probably incorrect long-range behavior of the JISP, because the one pion exchange is not manifestly implemented there.

A Wilsonian renormalization group (WRG) equation for nuclear current operators in two-nucleon systems is derived. Nuclear current operators relevant to low-energy Gamow-Teller transitions are analyzed using the WRG equation. We employ the axial two-body current operators from phenomenological models and heavy-baryon chiral perturbation theory, which are quite different from one another in describing small-scale physics. After reducing the model space of the operators using the WRG equation, we find that there still remains a significant model dependence at $\Lambda =200$ MeV, where Λ is the sharp cutoff specifying the size of the model space. A model-independent effective current operator is found at a rather small cutoff value, $\Lambda =70$ MeV. By simulating the effective current operator at $\Lambda =70$ MeV, we obtain a current operator based on a pionless theory, thereby arguing that an equivalence relation exists between nuclear current operators of phenomenological models and those of effective field theories.

It is a well-known fact that Dirac phenomenology of nuclear forces predicts the existence of large scalar and vector mean fields in matter. To analyze the relativistic self-energy in a model independent way, modern high-precision nucleon-nucleon ($\mathit{NN}$) potentials are mapped on a relativistic operator basis using projection techniques. Comparison of the various potentials at the level of covariant amplitudes produced remarkable agreement. It allows further calculation of the relativistic self-energy in nuclear matter in the Hartree-Fock approximation. Independent of the choice of the nucleon-nucleon interaction large scalar and vector mean fields of several hundred MeV magnitude are generated at tree level. In the framework of chiral effective field theory, these fields are dominantly generated by contact terms that occur at next-to-leading order in the chiral expansion. Consistent with Dirac phenomenology the corresponding low-energy constants that generate the large fields are closely connected to the spin-orbit interaction in $\mathit{NN}$ scattering. The connection to quantum chromodynamics sum rules is discussed as well.

We calculate unpolarized quark distribution functions and the $F_2$ structure functions for the proton and the neutron. The calculations are preformed in the light-cone frame. For the bare nucleon we have used three different distributions, namely, the spin-0 diquark, the spin-0 plus spin-1 diquark, and the no diquark models. By using perturbative QCD an initial gluon distribution is generated inside the core nucleon. The physical nucleon is assumed to be a superposition of the bare nucleon plus the virtual light-cone Fock states of baryon octets and decuplets and pseudoscalar meson pairs. The initial distributions are evolved. The $F_2$ structure functions calculated from the evolved distributions are compared with NMC and ZEUS results along with a CTEQ6M fit. Also, it is shown that the meson cloud is a contributing factor to sea-quark asymmetry and to Gottfried sum-rule violation.

We have observed nuclear excitation by electron transition (NEET) on ${}^{197}\mathrm{Au}$ by photoionization using synchrotron monochromatic x-rays around the $K\text{−}$absorption edge. By scanning the energy of the incident photons, we found that the NEET events had a steep edge at an energy ($40\pm 2$)eV higher than the $K$ edge; its width (FWHM) was $14\pm 9$ eV, quite narrower than that of the $K$ edge. A fine structure of the NEET events was also observed at photon energies higher than the NEET edge. This behavior is explained by the atomic transition from a particular $K$-hole state to the $M_1$-hole state, which resonantly excites the nucleus, and by an outgoing photoelectron with energy conservation.