With use of an unrestricted Hartree-Fock self-consistent-field cluster approach, the potential experienced by a muon in diamond has been investigated. The results strongly indicate that normal muonium is localized in the tetrahedral interstitial space. By using the calculated spin density and averaging it explicitly over the vibrational motion of the muon a quantitative explanation is obtained for the observed reduction of the hyperfine field as compared to free muonium.

The temperature and field dependence of spatial correlations and relaxation times are investigated in detail by Monte Carlo simulations for a two-dimensional Ising spin-glass model. There is no transition, but, in zero field, barrier heights and correlation range increase smoothly at low temperatures. This increase does not seem to be fast enough to explain experiments. In a field, barrier heights and the correlation length tend to a finite limit as $T\to 0$. Points in the $h-T$ plane with constant relaxation time satisfy $T\left(h\right)-T\left(0\right)\mathrm{}\propto h^{\frac{2}{3}}$ at moderately low temperatures.

The nonlinear response expected in a potassium point-contact device has been calculated with inclusion of the electron-phason interaction of Overhauser. With use of the theory of Kulik et al., to describe the point contact, a peak is found at low energy (at approximately 0.3 meV). This peak agrees well in energy, shape, and magnitude with an unexplained peak in the point-contact data of Jansen et al. A rather strong temperature dependence of the position, shape, and magnitude of this peak has also been found in the present calculations.

If axions exist, they contribute significantly to the present energy density. These axions have been collisionless and nonrelativistic since their appearance at ∼ 1 GeV. Hence axion density perturbations survive on essentially all scales, and once the axions are dominant, grow and in turn create and amplify baryon fluctuations. Axions can cluster into galactic halos even though the axion mass ≲${10}^{-2\mathrm{}}$ eV. If galactic halo matter is mainly axions, the Peccei-Quinn order parameter ≳${10}^{10}$ GeV.

A cosmological scenario where axions provide the dark matter in the universe is considered. Fluctuations in the axion-field energy density produced by domain walls and strings cause the appearance of "axion clumps" of masses of order ${10}^6{M}_{\odot }$ which most likely collapse to black holes by or at the time that the universe becomes axion dominated at $T\sim 10$ eV. These objects form the building blocks for the clustering hierarchy theory of galaxy and supercluster formation on scales up to ∼ 10 Mpc and ${10}^{15}{M}_{\odot }$.

It is shown that the Ashkin-Teller model has self-triality, which is a generalization of Kramers-Wannier self-duality proposed some time ago and illustrated with examples. In the Hamiltonian formalism, it means that the original Hamiltonian may be reexpressed in terms of either of two disorder variables without change of form and that the relation between all three variables is fully symmetric.

A new formulation is presented for the thermodynamics of the massive Thirring model in the attractive-coupling regime. A certain controversy between previous theories is resolved and an overall understanding of the thermodynamics is reached. In particular, it is shown that the soliton mass is discontinuous with the coupling constant at finite temperatures.

Topological theory predicts four charged and four neutral electroweak vector bosons, together with one neutral scalar boson. There is a single coupling constant $e$ allowing immediate prediction (up to radiative corrections), given the Fermi constant $G$, of a 75-GeV mass for left-handed charged vector bosons. The authors further predict vanishing of vector weak neutral-current coupling to charged leptons ($g_V=h_{\mathrm{VV}}=h_{\mathrm{VA}}=0\mathrm{}$). Dynamical assumptions motivated by meson spectra yield a vector boson spectrum whose lowest-lying four states correspond to the standard model with ${{sin}^2\theta }_W=\frac{1}{4}({M_{Z_0}}^2=\frac{4}{3}{M_W}^2)$.

With a PETRA energy scan in ≤30-MeV steps, the continuum production of open top quark up to 38.54 GeV is excluded. Over regions of energy scan from 29.90 to 38.63 GeV limits are set on the product of hadronic branching ratio and electronic width $B_h{\Gamma }_{\mathrm{ee}}$ for toponium to be less than 2.0 keV at the 95% confidence level. By a search for flavor-changing neutral currents in $b$ decay, models without a top quark are excluded.

The analyzing power, $A$, was measured in proton-proton elastic scattering with use of a polarized proton target and 28-GeV/c primary protons from the alternating-gradient synchrotron. Over the ${P_{\perp }}^2$ range of 0.5 to 2.8 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, the data show interesting structure. There is a rather sharp dip at ${P_{\perp }}^2=0.8\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ corresponding to the break in the elastic differential cross section at the end of the diffraction peak.

Using the CLEO detector at the Cornell Electron Storage Ring, the authors have measured the leptonic branching fractions, $B_{\mu \mu }$, of the $\Upsilon \mathrm{}\left(1S\right)\mathrm{}$, $\Upsilon \mathrm{}\left(2S\right)\mathrm{}$, and $\Upsilon \mathrm{}\left(3S\right)\mathrm{}$ to be 2.7±0.3±0.3%, 1.9±1.3±0.5%, and 3.3±1.3±0.7%, respectively. Combining these values of $B_{\mu \mu }$ with previous measurements of the leptonic widths of these resonances, the authors find the total widths of the $\Upsilon \mathrm{}\left(1S\right)\mathrm{}$, $\Upsilon \mathrm{}\left(2S\right)\mathrm{}$, and $\Upsilon \mathrm{}\left(3S\right)\mathrm{}$ to be 48±4±4, 27±17±6, and 13±4±3 keV.

If quarks and leptons are composite at the energy scale $\Lambda$, the strong forces binding their constituents induce flavor-diagonal contact interactions, which have significant effects at reaction energies well below $\Lambda$. Consideration of their effect on Bhabha scattering produces a new, stronger bound on the scale of electron compositeness: $\Lambda >750\mathrm{}$ GeV. Collider experiments now being planned will be sensitive to $\Lambda \sim 1-5$ TeV for both electrons and light quarks.

The ($p, {\Delta }^{++}$) reaction has been investigated in the framework of the distorted-wave Born approximation by use of the one-pion- and one-$\rho$-exchange transition interaction. The experimental data on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(p, {\Delta }^{++}){}_{}{}^6{}_{}{}^{}\mathrm{He}$ at 1.04 GeV are reproduced remarkably well, both in magnitude and in shape.

The features of fission-fragment angular distributions are shown to be sensitive to the occurrence of nonequilibrium processes such as quasifission. This conclusion is based on a quantitative analysis of the angular distributions of near-symmetric masses produced in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ + ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ reactions. The results are discussed in terms of the "extra-push" model of Swiatecki.

Double-differential cross sections for the reaction ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}(e, p_0){}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ were measured at eleven laboratory angles ranging from 42° to 138° with incident electron energies from 13 to 28 MeV. These have been decomposed into $E1\mathrm{}$ and $E2\mathrm{}$ components by use of a resonance model. Besides the large $E1\mathrm{}$ cross section, the $E2\mathrm{}$ strength is clearly separated at $E_x=14.9\mathrm{}$ MeV with the width of 5.1 MeV corresponding to the isoscalar giant quadrupole resonance.

Electronic alignment in molecular excitation, relative to a specific internuclear axis orientation, has been observed for the first time, enabling specific detailed checks of the quasidiatomic molecular-orbital model in kiloelectronvolt atom-molecule collisions. The alignment was determined from the polarization of ${\mathrm{L}}_{\alpha }$ radiation, resulting from the collision process ${{\mathrm{H}}_2}^{+}+\mathrm{He}\to {{{\mathrm{H}}_2}^{+}}^{*}+\mathrm{He}\to {\mathrm{H}}^{+}+\mathrm{H}\mathrm{}\left(2p\right)+\mathrm{He}$,, for specific laboratory scattering angles of ${\mathrm{H}}^{+}$. The results suggest that, as in many ion-atom systems, rotational coupling is the dominant excitation mechanism.

Transitions within the $2{}_{}{}^3{}_{}{}^{}P$ state of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ were measured to determine the parameters $C$, $D$, and $E$ which represent respectively the contact, dipole, and tensor terms in the hyperfine Hamiltonian. For the first time, the effect of core polarization on the hyperfine structure has been detected. The present results are $C=-4283.84\mathrm{}\left(1\right)\mathrm{}$ MHz, $D=-28.02\mathrm{}\left(6\right)\mathrm{}$ MHz, and $E=+7.08\mathrm{}\left(2\right)\mathrm{}$ MHz and are consistent with the theoretical values after the combined fine and hyperfine interactions with the $2{}_{}{}^1{}_{}{}^{}P$ state are taken into account in the analysis of the data.

The absolute energies of the Lyman-$\alpha$ lines of hydrogenlike iron have been measured with an accuracy of 90 ppm with use of a high-precision plane-crystal spectrometer calibrated directly with Co $K\alpha$ x rays. A value for the $1s$ Lamb shift of hydrogenlike iron has been deduced from this measurement.

Parametric decay of lower hybrid pump waves into daughter lower hybrid waves and electrostatic ion-cyclotron waves was observed above instability threshold power levels in a fully ionized plasma. The ion velocity distribution function was measured in time and space by the nonperturbing techniques of laser-induced fluorescence and ion optical tagging. Significant ion heating, $T_i$ up to $6T_{i0\mathrm{}}$, and cross-field transport were observed in the regime ${\omega }_0\gtrsim 12{\omega }_{\mathrm{pi}}$.

A mean-field theory for the diffusion-controlled cluster formation is presented by considering the competition among the different portions of a growing cluster for the incoming diffusive particles. This competition is shown to introduce a screening length which depends inversely on the density of the cluster. The Hausdorff dimensionality $D$ of these clusters is shown to be $\frac{(d^2+1)}{\mathrm{}(d+1\mathrm{})\mathrm{}}$ where $d$ is the Euclidean dimensionality. This result is in excellent agreement with that of the computer simulations of Witten and Sander and of Meakin.