We investigate the effects of direct nucleon-nucleon interactions in the ground state of pion-condensed neutron star matter within the σ-model formalism. We use a realistic description of asymmetric nuclear matter. The divergence of the critical density as $g_A$ approaches 1.0 is removed by including direct nucleon-nucleon forces. For the most realistic equations of state, we find a density interval with negative pressure from the critical density up to approximately 0.5 N/${\mathrm{fm}}^3$, preventing a pion condensate below this density. The most realistic equations of state are considerably softer than β-stable neutron star matter. The equations of state show similar behavior for both kinds of chiral symmetry breaking investigated in this calculation. The composition of the matter depends to some extent on the chiral symmetry breaking term in the Hamiltonian. The indicated proton percentage in the allowed density region is higher than 30.

The influence of relativity on the triton binding energy and the charge form factor of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is investigated employing the three-body Bethe-Salpeter equation with phenomenological separable potentials of rank one. For comparison these three-nucleon observables are also calculated in a purely nonrelativistic and two different quasipotential approaches. The Bethe-Salpeter results turn out to differ significantly from both the nonrelativistic and quasipotential ones. This may provide a framework in which the still existing discrepancy between theory and experiment can be lessened.

The fermion dynamical symmetry model is applied to an odd mass system via a strong coupling scheme and a direct comparison with the Nilsson model is made. Consequently, the deformed shell model Fermi-surface effect can be calculated from the fermion dynamical symmetry model as an approximate solution to the spherical shell model. Also, the finite particle number effect is studied with the fermion dynamical symmetry model; its effect is to renormalize the moment of inertia and deformation as well as to cause an attenuation of the Coriolis interaction.

The shifts in the energies of pairing vibrations due to the presence of valence nucleons are described in simple terms. Calculations are reported for the Z=50 isotopes and N=82 isotones and compared with experiment.

It is shown that the inclusion of pion, nucleon, and delta mass differences, and η-π mixing, in a coupled-channels treatment of the deuteron leads to small components of the wave function with isospin -1 and even isospin -2.

Similarities between cross sections and analyzing powers are reported for proton capture into 1$d_{5/2}$ orbits populating the ground state of ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ and the $3^{\mathrm{-}}$ second-excited state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$; for captures into 2$s_{1/2}$ orbits populating the ground state of ${}_{}{}^{29}{}_{}{}^{}\mathrm{P}$ and the $2^{+}$ first-excited state in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$; and for the 1$d_{3/2}$ orbits populating the ${(3/2\mathrm{}}^{+}$ first-excited state in ${}_{}{}^{29}{}_{}{}^{}\mathrm{P}$ and the $4^{+}$ second-excited state in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. The results are in reasonable accordance with the predictions of a direct-semidirect picture for nuclear capture reactions.

A previous measurement of the giant dipole resonance in Pb isotopes at an excitation energy of 68.5 MeV has been repeated at a lower excitation of 57.6 MeV with a mean spin of 14ħ. The large deformation observed at 68.5 MeV persists down to this low excitation energy and spin. A transition from the spherical ground state shape to the deformed excited state shape in a spin range 13–17 ħ is needed to fit the data with a consistent description of the giant resonance.

The differential cross section for electrodisintegration of the deuteron is calculated for near-threshold proton-neutron final states and backward electron angles in the GeV/c momentum transfer region. The calculation employs light-front-form Hamiltonian dynamics with a fixed number of nucleons for the strong interaction. The predicted cross sections are quite close to nonrelativistic calculations using only one-nucleon currents ( and thus disagree significantly with the data), but with quantitative differences in the kinematic region $Q^2$>20 ${\mathrm{fm}}^{\mathrm{-}2}$.

The P scheme of Casten, Brenner, and Haustein is used to suggest that nuclei will always become deformed when there are more than 10 valence nucleons of each type (protons and neutrons). Utilizing this scheme, necessary and sufficient conditions are also suggested for the onset of nuclear collectivity.

The speed of sound v is calculated for asymmetric nuclear matter within the general framework of a finite temperature Green’s function method with normal pair cutoff approximation and Skyrme interactions. A rather strong dependence of v on α, the asymmetry coefficient, is observed at high density. Causal violation of v at high density and/or high temperature is studied. This violation may be avoided if the Skyrme interaction parameters at high density may be readjusted to obey the conditions -1<d<0, $t_3$(3-${\alpha }^2$-2${\alpha }^2$${\chi }_3$)≥0, and -1<d<0,${\mathit{t}}_3$(3-${\mathrm{\alpha }}^2$-2${\mathrm{\alpha }}^2$${\mathrm{\chi }}_3$)≥0, and [(3${\mathit{t}}_1$+5${\mathit{t}}_2$)±α(${\mathit{t}}_2$-${\mathit{t}}_1$)]≤O. Implications of these

The direct transfer of four nucleons in reactions with superfluid systems is compared with the feeding of the same final channel by a successive transfer of correlated nucleon pairs. A quantitative analysis is carried out for the reaction ${}_{}{}^{120}{}_{}{}^{}$Sn${+}^{112}$Sn which shows the overwhelming dominance of the direct multiparticle transfer at bombarding energies below the Coulomb barrier. Results of simple estimates—supplemented by full coupled-channel calculations—provide orientation for selecting the experimental conditions which best exhibit the specific characteristics of the superconductive phase. The possibility of detecting an interference pattern between the two processes is also discussed.

We reexamine the feasibility of an experiment proposed by Skalsey to observe neutrinoless double-beta processes between pairs of single-beta emitters.

A realistic comparison is made of the two suggested decay modes that could be used to search for neutrinoless double-beta decay between pairs of single-beta emitters. Although both experiments are beyond current technical feasibility, the electron capture decay mode is superior. The dominant consideration is the background of bremsstrahlung photons.

It is shown that the Sn-Gd (N<82) nuclei form relatively poor F-spin multiplets so that the recently proposed method for predicting the spectroscopic factor ratios in the α-transfer reactions will provide a poor estimate. However, the method may apply to the good F multiplets in the Dy-Pt region (N<104).

Projectile-like fragments have been studied with high A and Z resolution for the damped reactions ${}_{}{}^{238}{}_{}{}^{}$U${+}^{40}$Ca, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ at 8.5 MeV/nucleon. These dinuclear systems exhibit widely different driving forces. Qualitative agreement between experiment and dynamical nucleon-exchange transport theory is obtained for the first and second moments of the fragment atomic (Z) and neutron (N) number distributions. However, systematic differences exist between the experimental and theoretical average values of Z and N suggesting the need for more realistic driving forces.

An extensive set of neutron scattering cross sections for four shape-transitional nuclei, ${}_{}{}^{190}{}_{}{}^{}$,192Os and ${}_{}{}^{194}{}_{}{}^{}$,196Pt, have been examined to test recent mean-field concepts which relate scattering potentials to those which bind single particle levels in nuclei. Scattering observables for each of these four nuclei have been separately and exhaustively analyzed to fix the potential strengths and their dependence on incident neutron energy. The results of these analyses revealed potentials quite different than the usual ‘‘Hartree-Fock type’’ potentials arising from global analyses at higher particle energies. A dispersion relation, based on the imaginary parts of the optical model potential, is applied in these analyses. Not only can the nonlinear energy dependencies observed in the scattering potential be described with this method, the potential can be extrapolated to negative energies where it is constrained to fit bound states in the neutron-plus-nucleus system. This is the first report of dispersion corrections for potentials from coupled-channels analyses of scattering from highly collective nuclei.

In-beam γ-rays from excited states of the neutron-rich ($T_z$=3) nucleus ${}_{}{}^{40}{}_{}{}^{}\mathrm{Cl}$ have been identified in a threefold coincidence experiment in which γ rays and light charged particles were observed. The resulting decay scheme is presented, and implications for the structure of low-lying levels in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Cl}$ are discussed in light of recent data from charge-exchange and β-decay work. The ordering of levels would seem to be quite different from the predictions of recent shell-model calculations.

Some heavy-ion resonance studies have suggested that entrance channel binding energies and, to a lesser extent, moments of inertia are important factors in determining whether or not a given entrance channel will exhibit resonances. To further investigate this question, two channels which lead to the ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ compound nucleus, ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{O}$, have been studied. When combined with the results from an earlier ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ investigation, an extensive set of data is now available to study the entrance channel dependence of heavy-ion resonance formation in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$.

Relativistic kinetic theory may be used to understand hot dense hadronic matter. We address the questions of collective flow and pion production in a three-dimensional relativistic fluid dynamic model and in the Vlasov-Uehling-Uhlenbeck microscopic theory. Collective flow and pion data point to a stiff equation of state. The effect of the nuclear equation of state on the thermodynamic parameters is discussed. The properties of dense hot hadronic matter are studied in Au+Au collisions from 0.1 to 10 GeV/nucleon.

We study effects of the mean field in hot compressed nuclear matter in the context of the Vlasov Uehling-Uhlenbeck theory. The expansion of a spherical distribution at different temperatures is studied along with collisions of Nb+Nb and Au+Au at lab energies from 50 to 1050 MeV/nucleon. In both the expansion and the actual heavy ion collision simulation, a transition behavior is seen only at the lowest temperature (T<10 MeV) or bombarding energy (E=50 MeV/nucleon), where the attractive part of the mean field is able to bind the expanding matter. At the lowest energy one thus sees the formation of a central residue, whereas at higher bombarding energies there is complete disintegration of the centrally colliding nuclei. The spectrum of emitted nucleons is found to be much hotter than the kinetic energy spectrum of the central emitting region. The extracted temperature slope parameters are in agreement with recent data.