The observed dramatic onset of backbending in ${}_{}{}^{104}{}_{}{}^{}$,106Pd isotopes is examined by carrying out a variational calculation of the high-spin yrast spectra. Our calculation reveals that the observed backbending effect in ${}_{}{}^{104}{}_{}{}^{}$,106Pd isotopes is intimately linked with the occurrence of sharp structural changes in the yrast spectrum of ${}_{}{}^{104}{}_{}{}^{}$,106Pd because of a sudden increase in deformation due to crossing of ${\mathit{h}}_{11/2}$, ±1/2 and ±(3/2 levels at the Fermi surface.

We show that the coupled channel equations are exactly transformed into the T matrix of the multistep process. The consistency with empirical models is discussed.

A number of recent papers have compared the ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ models for N¯N annihilation. We argue that a more consistent approach is to use both models together because they represent different aspects of quantum chromodynamics. In the approximation of the paper on which this Comment is based, our approach gives better agreement with data.

Using mass-separated sources, the $\beta$-decay properties of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Lu}$ and ${}_{}{}^{154}{}_{}{}^{}\mathrm{Yb}$ were investigated. Limits of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Lu}$ decay to the first $8^{+}$ and $6^{+}$ levels in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Yb}$ suggest a $7^{+}$ spin for the odd-odd parent; also delayed proton emission and an indication of delayed $\alpha$-particle emission were observed to follow ${}_{}{}^{154}{}_{}{}^{}\mathrm{Lu}$ $\beta$ decay. The $\beta$-decay branch of the $\alpha$-emitting nucleus ${}_{}{}^{154}{}_{}{}^{}\mathrm{Yb}$ was identified for the first time by the observation of one intense 133.2-keV $\gamma$ ray. This transition deexcites a $1^{+}$ 133.2-keV level in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Tm}$ which is fed by an allowed $0^{+}\to 1^{+}\beta$ transition with a $log\mathrm{ft}$ value of 3.6 ± 0.3.

We have observed a new isomer of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Sb}$ with a half-life of 16.7 min produced in fission. The absolute abundances of its gamma lines and its branching to ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}$ have been determined.

The nucleon mean free path in the intermediate energy region is estimated using various relativistic nuclear potential models. While the small effective mass in the relativistic models significantly enhances the theoretical values for the mean free path through Negele-Yazaki effect, it does not resolve the deviation from the experimental values extracted from the proton reaction cross sections on various targets.

This theoretical work represents the first stage in our efforts to establish an extensive list of nonfissile even-even nuclei located inside or near the valley of stability which might develop shape isomers. Our selection relies upon whether a secondary minimum takes place along an elongation axis in the potential energy surfaces of nuclei spread over the mass region $A<\mathrm{}208\mathrm{}$. These surfaces are determined through a joint use of the Hartree-Fock-Bogoliubov and Strutinsky methods. More than seventy nuclei located inside the region $40<A<\mathrm{}208\mathrm{}$ are suggested as possible candidates for shape isomerism.

There is strong evidence that the nucleus ${}_{}{}^{222}{}_{}{}^{}\mathrm{Ra}$ displays both quadrupole and octupole permanent deformations. The observed energy splitting between the associated even- and odd-parity rotational bands can be described in terms of superfluid tunneling in the space of nuclear shapes.

The properties of symmetric nuclear matter are investigated in the nonlinear relativistic mean field theory of nuclear matter. We consider the constraints imposed by four nuclear ground state properties on the coupling constants and on the equation of state at zero and at finite temperature. We find that the compression constant K(${\rho }_0$) as well as the temperature is irrelevant for the stiffness of the equation of state for $m^{\mathrm{*}}$(${\rho }_0$)≤0.7. The main point is that the relativistic mean field theory exhibits acausal and unphysical behavior for compressibilities below K(${\rho }_0$)=200 MeV. Every set of coupling constants with a negative quartic coupling constant c is unstable against small quantum fluctuations.

We report microscopic calculations of the equation of state for dense nuclear and neutron matter. The calculations are performed for five Hamiltonians: the Argonne $v_{14}$ and Urbana $v_{14}$ two-nucleon potentials, both alone and with the Urbana VII three-nucleon potential, and the density-dependent Urbana $v_{14}$ plus three-nucleon interaction model of Lagaris, Friedman, and Pandharipande. The beta-stable equation of state and neutron star structure are also calculated for three of the models. The models with the three-nucleon potential bracket the density-dependent model and are significantly stiffer than those with an unmodified two-nucleon potential only. The Argonne $v_{14}$ plus Urbana VII Hamiltonian produces a softening in the neutron matter equation of state localized around twice nuclear matter density which may indicate a neutral pion condensate.

Recently, it was observed that the O(6) limit of the interacting boson model for moderate boson number was equivalent to both a γ unstable rotor and a rigid triaxial rotor with γ=30°. Here it is shown that the proof given for this equivalence does not show that the eigenstates are equivalent in the two pictures but only that the subspaces for the low lying states are equivalent. A plausibility argument based on a dynamical symmetry of the γ=30° rigid rotor is given which suggests that the excited states of the O(6) system are not equivalent to the excited states of the rigid triaxial rotor. The ground states, however, are equivalent.

For a given partition of Hilbert space, we consider the projections of the eigenfunctions of the Hamiltonian onto the various subspaces. Average partial densities (smooth functions of energy) are defined by averaging the probabilities associated with such projection over neighboring eigenvalues. We aim at estimating the average partial densities reliably, starting from the traces and norms of the corresponding subspace-decomposition of the Hamiltonian. We employ the maximum entropy approach, and we define an ensemble of Hamiltonians having these traces and norms as mean values. Average partial densities are then calculated with the help of a generating function involving commuting and anticommuting variables. We present integral representations and asymptotic expansions for the average partial densities, and use the latter to compare our results with those obtained from shell-model diagonalization. We find satisfactory agreement, and discuss possible further applications.

Isovector E2 and M1 transitions from isobaric analog states of the N=29 isotones to low-lying states in the N=28 isotones are discussed by making use of the shell model. The $f_{7/2}^{n\mathrm{-}1}$j and the $f_{7/2}^n$+$f_{7/2}^{n\mathrm{-}1}$j configurations are assumed for the N=29 and N=28 isotones, respectively, where j denotes one of the $p_{3/2}$, $p_{1/2}$, and $f_{5/2}$ orbits. First, the model space is restricted to j=$p_{3/2}$ only, and it is extended to include all the $p_{3/2}$, $p_{1/2}$, and $f_{5/2}$ orbits, in order to study stepwise the role of the various wave function components. For the isovector E2 transitions, it is confirmed that the major components of the wave functions play a decisive role for the allowed transitions in the single-particle shell model and the use of the good isospin wave functions is indispensable for the forbidden ones. For the isovector M1 transitions, it is shown that the spin-nonflip $f_{7/2}$→$f_{7/2}$ transition, which is introduced by the neutron-excited components in the wave functions of the N=28 isotones, plays a very significant role: It gives rise to the important cancellation which is responsible for the strong suppression of the M1 transition strength in comparison with the simple shell-model prediction, and it becomes the leading term in the l- and j-forbidden M1 transitions. Similar discussion holds for the Gamow-Teller beta decays between the levels of the N=28 and N=29 nuclei.

The properties of clustered quark matter at finite temperature are studied. It is shown that clustered quark matter can exist only at low temperatures and then it is difficult to detect the new phase by high-energy heavy-ion collisions.

We perform a semiclassical analysis of the SO(3,1) S matrix. In particular, we discuss the near-far components of the amplitude and describe the nuclear rainbow scattering. We use the semiclassical inverse scattering theory to obtain the underlying potential, which is found to behave as $r^{\mathrm{-}1/2}$$e^{\mathrm{-}r/a}$ at large separations.

The one-dimensional Dirac equation is solved for a separable potential of the form of Lorentz scalar plus vector, (βg+h)v(x)v(x’). Exact analytic solutions are obtained for bound and scattering states for arbitrary v(x). For a particular combination of the values of g and h, degeneracy of the bound state occurs, and total reflection also takes place for a certain incident energy. The limiting case, in which v(x) becomes a delta function, is discussed in detail.

If the effect of α clustering due to the interaction of the excited correlated proton pair with correlated neutron pairs in medium and heavy nuclei were taken into consideration, quasiparticle energies would not be simply additive. The empirical values of the extra term δ(α) indicate that α correlations exist to a certain extent in these nuclei.

Using particle techniques, we have been unable to reproduce the resonant structure in the inelastic channel of the ${}_{}{}^{13}{}_{}{}^{}$C${+}^{17}$O reaction. The structure previously observed in the γ-ray yields for the 0.871-MeV transition is now believed to be due to a hydrogen contamination.

Multiple-particle γ-ray coincidence techniques have been used to establish the high spin structure of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Rb}$. Two ΔI=1 bands were found built on the $I^{\pi }$${=1\mathrm{}}^{\mathrm{-}}$ ground state and on the $I^{\pi }$${=(4\mathrm{}}^{+}$) isomeric state at 316.8 keV energy. Systematic of positive parity bands seen in the Br-Kr-Rb isotones with N=39 and 41 is discussed.