We demonstrate that average conduction-band electrons in a wide-band-gap insulator, Si${\mathrm{O}}_2$, are heated several electronvolts above the conduction-band edge at fields of 5 to 12 MV/cm. The electronic energy distribution appears to be stabilized at these high fields by energy-loss mechanisms other than LO-phonon scattering.

The polaronic transition of a two-dimensional electron system supported above a helium film was observed when the film thickness was reduced below 1000 Å in the temperature range $0.4<~T<~1$ K. The polaron is characterized by a mobility ${\mu }^{*}\sim 1$ ${\mathrm{cm}}^2$/V sec and a harmonic restoring parameter $K^{*}\sim {10}^{-7\mathrm{}}$ g/${\sec }^2$.

ac measurements on a "tunnel capacitor," in which small metal particles make tunnel junctions with one of the capacitor plates, reveal information about the electron tunneling process at the junctions. A simple zero-temperature model for the process is presented for the regime in which the Coulomb charging energy suppresses the conductance of the junctions. The prediction of the model that the capacitance and dissipation constant of the structure should scale as (frequency)/(applied ac voltage) is confirmed by the experimental results.

We present a new mechanism for explaining magnetocapacitance in the Andersonlocalized regime, based on the intrastate interaction within a localized state. It is shown that magnetocapacitance arises since a magnetic field suppresses the excitation from a singly occupied state to another singly occupied state. The calculated magnetic field dependence of magnetocapacitance is in good agreement with recent experiments by New et al.

We present a classical field theory which has a long epoch resembling the Friedmann universe despite the presence of a large negative cosmological constant. In its most plausible realization the model involves a massive third-rank antisymmetric-tensor gauge field. To be consistent with standard cosmology the mass must be extremely small and the only reasonable mechanism for generating it is a semiclassical tunneling effect.

To describe the irreversible growth of linear polymers, we introduce a new type of correlated walk, related to the zero—initiator-concentration limit of the kinetic gelation model. Our model simulates real polymer growth by permitting the walker to form the next bond from the unsaturated monomers at the neighboring sites of its present location. A heuristic kinetic argument of the Flory type suggests a fractal dimension $d_f=\frac{\mathrm{}(d+1\mathrm{})\mathrm{}}{2}$, in agreement with our Monte Carlo and series expansion results (including a logarithmic correction at the upper critical dimension $d_c=3\mathrm{}$).

Classical diffusion is studied on random chains with nearest-neighbor transfer rates having Gaussian distributions about sufficiently large systematic rates. Both the cases of static and dynamical white-noise randomness are considered, for symmetric as well as for asymmetric transfer rates. Probability densities for displacements along the chains are determined exactly in the continuum limit valid at long times, and are found to be Gaussian. The variance increases linearly in time for dynamical disorder and shows a qualitatively new quadratic growth for static disorder.

We report the results of the first direct search for grand-unified-theory magnetic monopoles with adequate sensitivity to detect a flux as small as the Parker flux limit. If stable monopole-nucleus bound states exist then the observed absence of monopole tracks in our 4.6×${10}^8$-yr-old mica detector places an upper limit of ${10}^{-17\mathrm{}}$ to ${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ on the flux of grand-unified-theory monopoles having velocity $3\times {10}^{-4\mathrm{}}c$ to $1.5\times {10}^{-3\mathrm{}}c$.

The curved—space-time generalizations of SU(5) grand unified theories are considered. The high-curvature limit of the effective gravitational and cosmological constants, as well as other coupling constants not present in flat space-time, is studied using renormalization-group methods. These effective coupling constants appear in the gravitational field equations and may have important cosmological implications.

The effect of an octupole component in the intrinsic mean field at high spin is demonstrated by a Woods-Saxon-Bogolyubov cranking calculation. The nature of nuclear rotation becomes nearly collective instead of collective plus single-particle, because octupole couplings with $\Delta l$ up to 3 "dilute" the high-$j$ shells. Theory is consistent with experimental data on ${}_{}{}^{222}{}_{}{}^{}\mathrm{Th}$ and could be tested further by studying the properties of rotating quasiparticles in neighboring odd-mass nuclei.

A distorted-wave impulse-approximation calculation for 50-MeV ${\pi }^{\pm }$ inelastic scattering to the $2_1^{+}$ state in ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ has been performed. The calculation shows greater sensitivity to the separate neutron and proton deformations than is seen with any other nuclear probe. A fit to the measured differential cross sections gives the value of 0.83±0.06 for the ratio of neutron to proton matrix elements for this state. This is in agreement with the values deduced with other probes.

The interaction mean free paths of He fragments emitted from two heavy-ion beams of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ at energy of 2 GeV/u have been measured with high statistics and were found to be approximately the same at all distances from their production points. Li and Be fragments, produced from known primary beams, also do not show any significant anomalous effect, within the statistics, in their mean-free-path values at any distance from their production point.

Cooperative effects in collisions of 60-84-MeV/u ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ projectiles with different target nuclei have been experimentally established through ${\pi }^0$ production, especially through the measurement of the apparent velocity of the pion source. Our method for the spectroscopy of neutral pions covers all angles and kinetic energies (down to zero). The exponential slopes in the spectra contain rather high Fourier components indicating the presence of short-distance phenomena in the collision dynamics.

The experimental vibrational energies for the stretching modes of the C${\mathrm{O}}_2$ molecule are used, with a recently developed method for generalizing the Rydberg-Klein-Rees inversion technique to polyatomics, to obtain a two-dimensional potential surface for nonbending C${\mathrm{O}}_2$. The resulting surface appears quite accurate; this demonstrates the ability of the method to obtain actual polyatomic potential surfaces and constitutes the first successful determination of a polyatomic potential surface by inversion of spectra.

A simple relationship transforms the theory of optical bistability into a theory of multimode instability and self-oscillation in a ring cavity excited between cavity resonances.

We present the first application of localization theory to plasma physics: Density fluctuations induce exponential localization of longitudinal and transverse electron plasma waves, i.e., the eigenmodes have an amplitude decreasing exponentially for large distances without any dissipative mechanism in the plasma. This introduces a new mechanism for converting a convective instability into an absolute one. Localization should be observable in clear-cut experiments.

Relativistic runaway electrons are detected by hard-x-ray and (photo)neutron emissions in low-density experiments with lower hybrid waves. During the rf pulse these signals can be explained in terms of the anomalous Doppler resonance on the primary lower hybrid waves which is effective on electrons having energy > 10 MeV. This effect is present independently of the density limit which determines the efficiency of the other resonance $\omega =k_{\parallel }{v}_{\parallel }$; the latter is responsible for electron tail enhancement (up to 300 keV) and for wave absorption, heating, and current-drive effects.

We present the first real-space observation of well defined single adsorbates: oxygen atoms forming the 2×1 structure on Ni(110). The sawtooth model is consistent with all experimental results. The structure consists of domains, separated in the $\left[1\mathrm{}\overline{1}0\right]$ direction by uncovered Ni ribbons 1½ surface unit cells wide. Such domain walls appear responsible for the $\theta =0.35\mathrm{}$ coverage of the saturated chemisorption structure.

We performed low-temperature specific-heat measurements investigating tunneling of H and D trapped by O impurities in Nb. The results yield the first experimental values of tunneling matrix elements for both H and D in a metal.

${\mathrm{H}}_2$O at 300 K has been studied up to 67 GPa by Brillouin scattering. A transition to a new form of ice occurs at 44 GPa. This is the tenth known solid form of ${\mathrm{H}}_2$O and may be the expected "symmetric-ice" structure.