By injecting the lower hybrid wave into the microwave discharge plasma at the electron-cyclotron resonance in the WT-2 toroidal device, the toroidal plasma current is generated, started up to $I_p\simeq 5$ kA, and sustained by rf power alone, without the Ohmic heating power (rf tokamak). This lower-hybrid-wave-driven current is produced only when high-energy tail electrons, which interact resonantly with the lower hybrid wave, are present in the initial electron-cyclotron resonance plasma.

A theory is presented for vacuum tunneling between a real solid surface and a model probe with a locally spherical tip, applicable to the recently developed "scanning tunneling microscope." Calculations for 2×1 and 3×1 reconstructions of Au(110) are in excellent agreement with recent experimental results, if an effective radius of curvature of 9 Å is assumed for the tip.

A theory is presented for the scanning vacuum-tunneling microscopy experiments performed by Binning et al. The tunnel current is obtained for different geometries and tip shapes. Lateral resolutions are 4-8 Å for distances from the tip to the sample ∼3.5-4.5 Å, effective tip radii ∼3-10 Å, 1-nA currents, and applied voltage ∼0.01 eV. The Au(110)(1×2) surface is analyzed and the experimental results discussed.

It is predicted that among the fcc, bcc, hcp, simple cubic, and $\beta$-tin phases, diamond will first transform to the simple cubic phase under a hydrostatic pressure of 23 Mbar. The absence of $p$ electrons in the core causes remarkably strong $s{p}^3$ bonding in diamond. This stabilizes diamond against the other five phases under high pressures. The study is carried out using ab initio pseudopotential theory within the local-density-functional formalism.

The first experimental investigation of nucleation, growth, and coalescence in a polymer solution near the critical point is reported. A large asymmetry is observed in the kinetics of phase separation although the coexistence curve itself is only slightly asymmetric near the critical point. The observed effects are explained by the strong composition dependence of viscosity, diffusion coefficient, and correlation length in polymer solutions.

Low-energy electron diffraction has been used to study the dynamics of formation of oxygen $p(2\mathrm{}\times 1)$ superlattice structure on a W(112) surface at a half-monolayer coverage. The ground state of the $p(2\mathrm{}\times 1)$ structure is twofold degenerate and the nonconserved long-range order associated with this structure was found to grow linearly with time in the earlier stages. This behavior is interpreted with use of the domain-growth theory proposed by Lifshitz and by Allen and Cahn. The temperature dependence of the growth rate obeyed an Arrhenius law for $\frac{T}{T_c}<~0.4$.

For a large class of models, the connection between roughening and facet formation is explored in detail. It is shown that there is a universal jump in the crystal surface curvature at the roughening transition. Explicit calculations within one model yield facet shapes and a universal exponent describing crystal shapes near a facet. Hyperscaling arguments provide facet sizes for generalized solid-on-solid models.

The phase diagram of electrons on films of helium is investigated with use of simple qualitative ideas. It is shown that several new very interesting experimentally accessible regimes are possible. Quantum effects can be important and a new fluidlike state ($n\to 0, T\to 0$) appears.

The band structure of Mn-based Heusler alloys of the $C{1}_b$ crystal structure (MgAgAs type) has been calculated with the augmented-spherical-wave method. Some of these magnetic compounds show unusual electronic properties. The majority-spin electrons are metallic, whereas the minority-spin electrons are semiconducting.

The low-energy regime (0.1-0.3 eV) of the electron-energy-loss spectrum from a clean Cu(100) surface has been measured. The experimental data show excellent agreement with predictions from a jellium calculation of the response function $g(q_{\parallel }, \omega )$. The weak inelastic signal derives from long-range excitation of electron-hole pairs; the surface potential and the spatial variation of the potential from the probing electron are the prime momentum sources.

Photoexcitation of trans - but not cis -polyacetylene, results in the appearance of strongly-ir-active local modes at 1370 and 1260 ${\mathrm{cm}}^{-1\mathrm{}}$. This observation demonstrates that the photogeneration of self-localized charge carriers is unique to the trans isomer. In spite of their localization the kinetic mass of these photocarriers is small, $M_c\simeq \mathrm{}(1-2.5)m$, a result which is in quantitative agreement with calculations based on single-chain models.

The long-time behavior of a system of two nonlinear oscillators interacting through a linear continuous string is investigated numerically. The string is treated exactly (no spatial lattice). It is found that such classical systems display many features normally associated with quantum mechanics, such as a phase space which breaks up into an infinite number of finite-size cells of ergodic motion.

A quantitative formulation of the uncertainty principle, based on Deutsch's idea of using entropy as a measure of uncertainty to remove the inadequacies of the standard treatment, is presented. This uncertainty in general involves the resolution of the measuring device.

It is shown how Euclidean expectation values in quantum chromodynamics may be calculated by Monte Carlo simulation of an equation of the diffusion type with a drift force that is a local function of gluon and pseudofermion fields. This allows a local updating procedure.

By use of dimensional reduction from a six-dimensional Riemannian manifold to four Euclidean dimensions, the different topological configurations which arise in a Yang-Mills-Higgs system have been analyzed. A new class of instantons in this model is characterized by the Hopf index and the equations of motion are given as a first-order system of differential equations. The analogies with superconductivity are also pointed out and an explicit expression for the action is given.

All previous attempts to put supersymmetry on the Wilson lattice have encountered difficulties because supersymmetry necessarily closes on the Poincaré group, while the Wilson lattice is not Poincaré invariant. This difficulty is overcome by construction of a gauge theory defined on a random supersymmetric lattice. New features are found, and the usual supersymmetric Yang-Mills theory is recovered in the continuum limit (infinite density of sites). Comments are included on how to use this method to calculate possible dynamical breaking of supersymmetry.

In view of the almost established triviality of ${\varphi }^4$ in four dimensions it is conjectured that the mass of the Higgs particle in the minimal model is bounded by an amount that can be estimated without the knowledge of the physics at shorter distances. A possible numerical experiment which could give a nonperturbative estimate for the bound is proposed.

Cross sections for monopole-catalyzed nucleon decays (Rubakov process) receive a velocity-dependent correction factor in matter due to an extra angular momentum carried by the monopole-electric-charge system. This leads to a strong suppression factor for slowly moving monopoles in detectors using heavy elements.

It has been observed that the spontaneous-emission lifetime of Rydberg atoms is shortened by a large ratio when these atoms are crossing a high-$Q$ superconducting cavity tuned to resonance with a millimeter-wave transition between adjacent Rydberg states.

Charge-state distributions of 130-MeV Br ions have been measured as a function of incident ion charge for a preequilibrium- and an equilibrium-thickness carbon target. These measurements lead to a relatively simple interpretation of the charge-exchange processes and are compared with the predictions of the Bohr-Lindhard and Betz-Grodzins models.