The effect of the proton-proton Coulomb interaction in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ground state is investigated. The rms radii, first-order and second-order Coulomb energy shifts, the validity of the hyperspherical approximation, and the various trinucleon densities are examined.

A practical number-conserving method of treating pairing correlations is proposed. The theory is formulated in a form having clear correspondence with quasiparticle theory and, moreover, it works well even in the weak pairing limit. Various matrix elements are approximately expressed in terms of the occupation probabilities containing the blocking effects within the number-conserving framework. The exact occupation probabilities can be used in the case of a constant pairing force. The present method is able to take the place of previous fixed-number BCS methods and is suitable for treating residual correlations further. Application to the cranking model is discussed.

To see how closely an interacting-boson-model-like model can be approached, we systematically develop a similarity transformation that unitarizes the simple correspondence version of the Dyson boson mapping of the Ginocchio SO(8) model. For a large region of Hamiltonian parameter space, a one-body plus two-body Hermitian boson Hamiltonian of the interacting-boson-model form is achieved. The similarity transformation consists of a dynamical part and a normalizing part. The dynamical transformation results in a one-body plus two-body Hermitian Hamiltonian and simple transition operators. The normalizing transformation commutes with the dynamically transformed Hamiltonian. This enables the transition rates to be calculated without introducing dual bases. However, the resulting boson model differs from the phenomenological interacting boson model in that transition rates are not calculable from the absolute squares of matrix elements. Dynamically transformed operators are given explicitly, and normalizing transformations for SO(6) and seniority limits are obtained in closed form.

We have done a renormalization group analysis of the phase transition in highly viscous finite nuclear matter with an energy functional consisting of a semiclassical kinetic energy term and a Skyrme-type term plus a simple surface term as the potential. We have also calculated the critical exponents for the transition.

The correspondence between the SD fermion and sd boson spaces is investigated. A method is discussed for generating boson images of fermion Hamiltonians. The boson Hamiltonians obtained are at most two-body and, in general, non-Hermitian. Applications to a quadrupole-quadrupole interaction are presented. E2 operators are also studied. Fermion spectra and E2 matrix elements are well reproduced in the boson space.

Real-time finite temperature Green’s function methods with pair cutoff approximations are applied to the calculation of the equation of state of symmetric nuclear matter. The liquid-gas and the superconducting second-order phase transitions of nuclear matter are studied using, respectively, the normal and abnormal pair cutoff approximations. Several versions of the Skyrme effective interactions are employed. Significant differences are found between the pressure-density isotherms at finite temperature given by different Skyrme interactions, although they give quite similar ground state nuclear matter properties. The critical temperatures $k_B$$T_c^{\mathrm{}\left(1\right)\mathrm{}}$ for the liquid-gas phase transition given by various Skyrme interactions range from ∼15 to ∼20 MeV. A strong dependence of $k_B$$T_c^{\mathrm{}\left(1\right)\mathrm{}}$ on the combination 3$t_1$+5$t_2$, $t_1$ and $t_2$ being two parameters of the Skyrme interaction, is observed. For nuclear matter at normal density, nonvanishing energy gap is obtained only for the Skyrme interactions SkI and SkVI. The critical temperatures for the superconducting second-order phase transitions for these two cases are, respectively, 0.5 and 0.345 MeV. Dependence of the energy gap on the nuclear matter density is discussed.

A Thomas-Fermi equation, which includes a hard-core effect, is obtained and solved. The hard-core effect is simulated by using an effective kinetic energy which diverges at high densities and induces an approximate saturation in the fermion assembly.

The structural instabilities or general nonthermodynamic phase transitions of the time-dependent Hartree-Fock flow on the Bloch sphere are investigated for different SU(2) model Hamiltonians by means of a simple geometrical construction. In particular, the generalized Lipkin-Meshkov-Glick model is found to exhibit a variety of instabilities, opposite to the standard Lipkin-Meshkov-Glick model which possesses only one ground-state (thermodynamic) phase transition. The relationship between the fixed points of the time-dependent Hartree-Fock flow and the tangency points between energy surfaces and the Bloch sphere is established. It is found that different Hamiltonians of the class under study give rise to flow patterns whose invariant sets may contain either rotations or librations, which in turn may be degenerate as well as nondegenerate, in contrast to previously investigated models.

New calculations including an approximate treatment of Coulomb effects in the α-induced deuteron breakup reaction are compared with existing experimental results at $E_{\mathrm{d}=6\mathrm{}}$ and 7 MeV and with new measurements at $E_{\alpha }$=11.3 MeV. The α-p Coulomb potential allows the coupling to the ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$ np channel which can give rise to a sharp peak in the $E_{\mathrm{np}=0\mathrm{}}$ region. We display the relevance of the two-body final state interactions and, in particular, of the isospin forbidden np singlet interaction, both theoretically and experimentally.

Results of the first experimental search for the excitation of discrete final states following exclusive (${\pi }^{\mathrm{-}}$,p) reactions are reported. The measurements include differential cross section at ${\mathrm{theta}}_{\mathrm{lab}=25\mathrm{}}$° for (${\pi }^{\pm }$,p) reactions on ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ at $T_{\pi }$=120 MeV and (${\pi }^{\mathrm{-}}$,p) on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at $T_{\pi }$=145 MeV. The (${\pi }^{\mathrm{-}}$,p) reactions yield peaks with dσ/dΩ≤1 μb/sr compared to 7–22 μb/sr for peaks from (${\pi }^{+}$,p) reactions. The shape of the continuum in an excitation energy range of 10–40 MeV was found to be independent of pion charge and target. The ratios of (${\pi }^{+}$,p)/(${\pi }^{\mathrm{-}}$,p) averaged over excitation energy and the ratios of the same reaction on different nuclei are presented. The magnitude of the proton yield in the low excitation continuum is more than 20 times larger for ${\pi }^{+}$ than for ${\pi }^{\mathrm{-}}$, which supports a two-nucleon absorption model including pion charge exchange.

An excitation function from $T_{\pi }$=50 to 120 MeV at ${\mathrm{theta}}_{\mathrm{lab}=35\mathrm{}}$° and an angular distribution at 60 MeV have been measured for the pion double-charge-exchange reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{\mathrm{-}}$)${\mathrm{}}^{12\mathrm{O}(\mathrm{g}.\mathrm{s}.\mathrm{})\mathrm{}}$. The cross section is found to decrease with increasing energy. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ excitation function and the angular distribution are very similar in shape to those of the double-isobaric-analog-state transitions observed for ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, but the magnitude is a factor of 6 smaller.

High-resolution laser spectroscopy has been performed on an atomic beam of natural erbium isotopes. The isotope shift in the 582.7 nm transitions [${4\mathrm{f}}^{12}$${6\mathrm{s}}^2$(${\mathrm{}}^3$${\mathrm{H}}_6$)→${4\mathrm{f}}^{12}$(${\mathrm{}}^3$${\mathrm{H}}_6$)66(${\mathrm{}}^3$${\mathrm{P}}_1^0$)J=7] for the pairs of ${}_{}{}^{162}{}_{}{}^{}$,164,166,167,168,170Er I was obtained with an accuracy of about 4 MHz. Relative changes of mean-square nuclear charge radii δ〈$r^2$〉 for these isotopes were thus deduced. The isotope shift in ${}_{}{}^{167}{}_{}{}^{}\mathrm{Er}$, obtained from the well-resolved hyperfine components, shows similar even-odd staggering effect in δ〈$r^2$〉 found in the nearby elements.

Excitation functions of the analyzing power $A_y$(theta) for neutron elastic scattering from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were measured at two angles in the neutron energy range from 15.6 to 16.5 MeV. The results do not support the existence of the narrow resonance in n${\mathrm{-}}^{12}$C scattering located at $E_{\mathrm{n}}$=16.1 MeV that was observed recently by Benetskii et al. through similar $A_y$(theta) experiments. Instead, the data are moderately well described by our previous n${\mathrm{-}}^{12}$C phase-shift analysis, which gave no evidence of a pronounced narrow resonance anywhere between neutron energies from 15.5 to 16.5 MeV.

The hybrid model for precompound decay is applied to the calculation of neutron spectra following the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ bombardment of ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ at 220, 292, ${(}^{20}$Ne), and 300 ${(}^{12}$C) MeV. Results are compared with experimentally deduced angle integrated spectra and with results of the Boltzmann master equation. Both models give excellent agreement with experimentally deduced spectra.

A new procedure has been developed for projecting out nondegenerate, linearly independent orthonormal states when calculating coefficients of fractional parentage with an iteration formula. This procedure is free from the buildup of numerical errors which vitiates the conventional techniques in cases where large dimensions are encountered. As a first application, coefficients of fractional parentage for the complete j=(7/2) shell in an isospin formalism have been generated for use in large-scale shell-model calculations.

That the size of a nucleon increases when bound is shown to follow in first order from the attractive nature of the binding potential. We give two simple demonstrations of the connection of size change with the sign of the external potential, the generality of which helps to connect a wide class of successful explanations of medium modifications of the form factor and of the European Muon Collaboration effect.

The production of hypernuclei in the continuum above hyperon binding is calculated by a pole graph method. The continuum can exhibit a structure which complicates the interpretation of hypernuclear spectra, especially in the case of Σ hypernuclei.

A first calculation of polarization in the ${\pi }^{\mathrm{-}}$p→ηn reaction at √s <1600 MeV is presented. The calculation is based on a model that requires a set of πN elastic scattering phase shifts as an input and hence is able to distinguish among various πN phase-shift analyses if the polarization data are available.

This paper presents an interesting observation, i.e., Koba-Neilsen-Olesen-type scaling in the multiplicity distribution of medium energy protons emitted as a result of ${}_{}{}^{12}{}_{}{}^{}\mathrm{AgBr}$ (emulsion) and central ${}_{}{}^{24}{}_{}{}^{}\mathrm{AgBr}$ (emulsion) interactions at 4.5A GeV/c and p¯-AgBr (emulsion) reactions at 1.4 GeV/c. In all cases, the experimental points lie on the universal curve which can be fitted with a Koba-Neilsen-Olesen-type scaling function ψ(Z=${\mathrm{n}}_{\mathrm{p}}$/〈${\mathrm{n}}_{\mathrm{p}}$〉)=(4Z+${4\mathrm{Z}}^3$-${5\mathrm{Z}}^5$+0.${35\mathrm{Z}}^7$)exp(-2.957Z). .AE 57Z). .AE

Realistic calculations of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Xe}$ level density, in the framework of a microscopic Nilsson-BCS formalism with blocking effect, reproduce the observed cumulative numbers of unbound levels with spin (1/2), (3/2), (5/2), (7/2), and (9/2) in the energy range 4.0–4.5 MeV. By contrast, the statistical estimate for the parity distribution of the same excited states disagrees with the experimental information, thus demanding an improved theoretical treatment of parity effects.