A mechanism for dynamical generation of fermion mass in three dimensions is proposed. Spontaneous breaking of parity as well as certain flavor symmetry is discussed.

A measurement of continuum dimuon production in proton-copper collisions at 800-GeV incident energy is presented. The dimuons observed in this experiment cover the mass range from 6.5 to 18 GeV near y=0 in the proton-nucleon center-of-momentum frame. Scaling forms of the cross section for the continuum are compared with the results of other experiments in the context of the parton model and quantum chromodynamics. The present limitations of such scaling comparisons are discussed.

A numerical three-dimensional solution of the equations of relativistic hydrodynamics with Landau-type initial conditions has been obtained. Using an equation of state consistent with lattice-QCD calculations, the rapidity and transverse-momentum distributions are calculated for O+Au collisions at 200 GeV/nucleon. Satisfactory agreement with data is obtained with an initial temperature $T_i$=220 MeV corresponding to a mixed quark-gluon–hadron phase. A pure hadron phase is within this formalism inconsistent with the data.

High-spin states up to I${=31\mathrm{}}^{\mathrm{-}}$ have been studied in the ${}_{}{}^{218}{}_{}{}^{}\mathrm{Ra}$ nucleus and the staggering sequence of levels of positive and negative parity persists up to highest level. This observation supports the idea that in some nuclei the high-spin excitations may primarily be dominated by deformations which do not conserve the intrinsic parity (such as octupole, λ=3, and higher odd-λ multipolarities) rather than by the ‘‘usual’’ quadrupole (λ=2) and possibly higher even-λ multipolarities.

The widely used continuum discretized coupled-channels (CDCC) method for approximate calculations of three-body systems is discussed as a truncation of a Faddeev formulation in angular momentum space. A set of coupled equations is presented for converting a CDCC solution into a full solution of the original Schrödinger equation. A practical iterative procedure for solving the equations is outlined, based on the ‘‘distorted Faddeev equations’’ of Birse and Redish.

The bound-state photoabsorption spectra for Rydberg states of lithium and strontium in a magnetic field are evaluated and compared with that of hydrogen. The line positions and oscillator strengths depend strongly on the Rydberg electron’s interaction with the ionic core. The position of the peaks in the Fourier transform of these spectra, for short times, are insensitive to the strength of the core interaction but the relative intensities of the peaks do depend on this interaction. The energy spacing of ∼0.64${\omega }_c$ is seen in the Fourier transform of all of the spectra.

A systematic method is outlined for constructing workable approximations to the joint probability distribution scrP(ψ,ξ) of amplitude ψ and spatial gradient ξ of an active or passive scalar field that is advected by a prescribed isotropically distributed stochastic velocity field and subjected to molecular diffusion. scrP(ψ,ξ) is sampled along fluid-element paths, and closure is obtained by taking a multivariate-Gaussian reference field ${\mathrm{\psi }}_0$(x) and distorting it locally in x space so that it exhibits the current scrP(pxi,ξ).

We introduce a microscopic model for the phase separation in block copolymers and carry out Monte Carlo simulations in two dimensions. We find that the equilibrium structure function satisfies a scaling relation with $D_{\mathrm{eq}}$, the thickness of the microdomains. We also find that $D_{\mathrm{eq}\mathrm{\sim }{N}^{\theta }}$, where N is the chain length and θ=(1/2 in the weak-segregation limit, in agreement with calculations in a cell-dynamics model. This suggests that the microscopic and the continuum models of block copolymers are in the same universality class.

We show that optical second-harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. The technique applied to liquid-crystal monolayers on rubbed and unrubbed substrates indicates that two different surface-originated mechanisms are effective in aligning a liquid-crystal film: One is based on molecular interaction and the other on elastic interaction.

One of the oldest unresolved problems in physics is the mechanism of charge exchange between contacting surfaces when at least one of them is insulating. We describe a new technique, using force microscopy, for studying this problem with greater lateral resolution than has been previously possible. The force microscope is shown to have 0.2 μm lateral resolution and the sensitivity to detect 3 electronic charges. In contact-charging experiments between the microscope tip and polymethyl methacrylate, the charged region was much larger than the expected contact area and bipolar charge exchange was observed.

The isotopic composition of the flux of sputtered neutrals was monitored for very low primary beam fluences (≲1×${10}^{15}$ ${\mathrm{Ar}}^{+}$ ions/${\mathrm{cm}}^2$) and different emission angles (0° to 60°) by means of secondary neutral mass spectrometry. Initially, the emitted material is enriched in the lighter isotopes by a factor of about 1.05 for ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$${/}^{76}$Ge and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$${/}^{100}$Mo. This initial enrichment is independent of the emission angle and gradually decreases during sample erosion. A steady-state value is reached upon sputter removal of a layer of roughly 15 nm.

Measurements of the time-differential decay of the collective nuclear excitation in yttrium iron garnet have been performed to observe the (002) pure nuclear reflection versus the splitting within two d sites. Even when the energy levels of the two sites are identical, the reflectivity amplitude does not vanish. This is a new realization of a pure nuclear reflection. It arises in case of nuclear level crossing of two d sites because their eigenvectors are not identical.

Double-peaked ${\mathrm{L}}_{\mathrm{III}}$-edge x-ray-absorption (XA) spectra are reported for various compounds of Np. Related high-pressure studies of ${\mathrm{UO}}_3$ support the idea that these peaks are due to core-ionized final states with different 5f occupancies reflecting the correlated electronic ground state. The weighted mean ${\mathrm{L}}_{\mathrm{III}}$-XA positions shift to higher energies with decreasing 5f occupancy and, for nonmetallic compounds, depend monotonically on the respective ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$ Mössbauer isomer shifts. Deviations from this correlation are observed for metallic compounds due to conduction-electron contributions to the isomer shift.

An effective-gauge-field-theory model of a doped Mott insulator is generalized so as to be electromagnetically gauge invariant. It is proposed that three Chern-Simons terms enter, one involving the spin gauge field, another the electromagnetic field, and the third a coupling between them. A model-independent topological argument is given for the quantization of the coefficients of these Chern-Simons terms. Physical consequences are noted, including a possible relationship between the Hall fraction and the effective spin of the excitation quanta.

By stochastic simulation, we investigate the spatial pattern in the biological system composed of three competing species. Topological defects are introduced to explain the pattern formation in this system. The spatial dimension d determines the nature of defects such as kinks, vortices, and strings. When d=2,3, the system approaches the stationary state, where the peculiar defect configuration is found.

We consider the 3D Schrödinger equation with a potential having no spherical symmetry and show that such a potential can be constructed from the scattering operator by using the solution of a Fredholm integral equation. The Fredholm integral operator presented is compact and self-adjoint; its eigenvalues are symmetric about 0 and lie in [-1,1].

Using Lüscher’s small-volume expansion, mass spectrum and deconfining temperature of SU(3) gauge theory are evaluated. Including nonperturbative features by restoring symmetries which were broken in perturbation theory we obtain results which are valid up to intermediate volumes. The mass spectrum obtained is in good agreement with the perturbative results for small volumes, and with Monte Carlo data in medium-sized volumes. Using asymmetric volumes we are able to estimate the deconfining temperature and find reasonable agreement with Monte Carlo calculations.

We have studied electron capture followed by delayed fission in ${}_{}{}^{234}{}_{}{}^{}\mathrm{Am}$. The half- life of ${}_{}{}^{234}{}_{}{}^{}\mathrm{Am}$ was determined to be 2.32±0.08 min and the measured ratio of delayed fissions to plutonium K x rays was (6.6±1.8)×${10}^{\mathrm{-}5}$. The observed fissions were unequivocally assigned to an electron-capture–delayed-fission process in americium by coincidence measurements between the K-capture x rays and the subsequent fission.

Emission patterns of neutrons from damped ${}_{}{}^{139}{}_{}{}^{}$La${+}^{40}$Ar reactions at $E_{\mathrm{lab}=400\mathrm{}}$ and 600 MeV, mostly consistent with sequential evaporation from accelerated fragments, reveal the existence of a high-energy component at all kinetic energy losses. The average multiplicity associated with this nonequilibrium component is found to scale with the radial kinetic energy at contact, with a threshold of $E_{\mathrm{rad}\mathrm{\approxeq }2}$ MeV/nucleon. Boltzmann-master-equation and Fermi-jet models disagree with the data, the latter model requiring enhanced high-momentum components.

Coulomb explosion experiments have been carried out on both the dihelium cation ${\mathrm{He}}_2^{+}$ and the corresponding doubly charged molecule ${\mathrm{He}}_2^{++}$ yielding bond-length distributions for each species. These measurements provide the first experimental evidence for the bond length of ${\mathrm{He}}_2^{++}$. The most probable value of the measured bond-length distribution is 0.75±0.2 Å. We also determine the lifetime to be longer than 5 μsec. This demonstrates the suitability of the Coulomb explosion method to the study of structures of short-lived, highly reactive, rare, or otherwise exotic molecules.