Fermi radii and velocities are determined by deconvoluting de Haas—van Alphen data. Comparison of these data with accurate augmented—plane-wave band-structure results establishes the reliability of the augmented—plane-wave calculations and allows a determination of the anisotropic many-body enhancement factor $\lambda \left(\overrightarrow{\mathrm{k}}\right)$. The Fermi-surface average $〈\lambda 〉$ of 1.33 suggests a large electron-electron contribution. Our anisotropic $\lambda \mathrm{}\left(k\right)\mathrm{}$ provide a detailed test and guide for model calculations of many-body enhancement.

A dominant surface state has been observed on the W{110} surface by photoemission with 16.8, 21.2, and 40.8 eV photons. For the first time an experimental surface band structure is presented covering the entire surface Brillouin zone. Theoretical calculations of the surface density of states on W{110} are found to be in good agreement with experiment, and allow an assignment of the surface state. The calculations show that this state, which has split off a bulk-band edge into an absolute band gap, is transferable to the W{001} plane.

We show that the exchange reaction between Al and GaAs at the microscopic interface produces a charge redistribution in two stages which determines Schottky-barrier formation.

We report the low-field ac susceptibility from 16 Hz to 2.8 MHz on the dilute spin-glass Ag:Mn in the vicinity of the glass temperature, $T_G$. Within experimental error $T_G$ is frequency independent. We also report electron-spin-resonance measurements in the same samples at 1.6 and 9.1 GHz. The differences in the ESR data at two frequencies appear to be due to the different fields for resonance and not to the different measuring frequencies.

The elementary excitations of the anisotropic chain in finite fields are calculated for the case $\left|\Delta \right|<~1$ and they are shown to dominate the weight function ${{\chi }_{\mathrm{zz}}}^{\prime \prime }(k,\omega )$ for small $k$. Several experiments are suggested to prove their observability.

Using the Vlasov equation, we show that massive galactic halos cannot be composed of stable neutral leptons of mass ≲ 1 MeV. Since most of the mass in clusters of galaxies probably consists of stripped halos, we conclude that the "missing mass" in clusters does not consist of leptons of mass ≲ 1 MeV (e.g., muon or electron neutrinos). Lee and Weinberg's hypothetical heavy leptons (mass ≲ 1 GeV) are not ruled out by this argument.

The energy of a linearly perturbed system is shown to verify a nonlinear first-order differential equation in the semiclassical limit. Solutions of this equation are compared to the exact energies, for a quartic oscillator.

We report a theroetical prediction of a new feature in the spectrum of light scattered from a fluid in a nonequilibrium stationary state with a temperature gradient. The spectrum is not symmetric in the frequency shift and the Brillouin components have different intensities. The phenomenon is linked to the breaking of time-reversal symmetry and to the appearance of a static correlation function between momentum and number densities which is zero in equilibrium, but has a $\frac{1}{k^2}$ dependence in the stationary state. We suggest a light scattering experiment by means of which these predictions can be verified.

The quantum-chromodynamic predictions are computed for production of large-transverse-momentum lepton-antilepton pairs from $q\overline{q}$ scattering (which is relevant to ${\pi }^{-}p$ or $\overline{p}p$ collisions). A simple formula not involving the parton distributions is derived for two of the three coefficients describing the angular distribution.

I show that parton transverse-momentum effects can be included in factorized quantum-chromodynamics inclusive cross sections, but that factorization is maintained only if the transverse-momentum variable which is held fixed is independent of the scale of the parton momentum. I also emphasized that other nonperturbative effects can be just as important as the transverse momentum.

Quantum-chromodynamic sum rules are derived which are sensitive to resonance contributions and in fact allow one to compute leptonic decay widths and masses of low-lying resonances. The crucial point is the inclusion of power corrections which are related to the vacuum structure of quantum chromodynamics.

Measurements of the fluctuations in local velocity in fluid motion between a rotating inner cylinder and a fixed outer cylinder are reported for rotation rates up to $67R_c$, where $R_c$ is the critical Reynolds number for Taylor instability. The Reynolds number $R_t$ for which the transition from periodic or quasiperiodic to aperiodic flow occurs depends strongly on aspect ratio ($\Gamma =\mathrm{fluid}\mathrm{height}/\mathrm{gap}$): $R_t\simeq 22R_c$ for $\Gamma =20\mathrm{}$; $R_t\simeq 26R_c$ for $\Gamma =80\mathrm{}$. For $\Gamma \gtrsim 25$ a sharp periodic component reemerges in the power spectrum for $28R_c\lesssim R\lesssim 36R_c$.

Ion-temperature results are deduced from Doppler-broadening measurements of the $K\alpha$ ($1s-2p$) resonance line emitted from heliumlike iron impurity ions in the hot central core of PLT (Princeton Large Torus) tokamak discharges. The measurements were performed using a high-resolution Bragg-crystal spectrometer with a multiwire proportional counter.

Saturation of stimulated Brillouin scattering has been observed in the interaction of long-pulse C${\mathrm{O}}_2$-laser radiation with underdense hydrogen plasma at intensities of ≤${10}^{13}$ W/${\mathrm{cm}}^2$. The stimulated Brillouin scattering is strongly modulated with average long-time reflectivity approximately half the peak value. The maximum reflectivity measured was 60% and wave breaking is postulated as the principal saturation mechanism.

Experimental results are presented on the growth, diffusion, and saturation of magnetic fields spontaneously generated by the interaction of intense microwave radiation with an inhomogeneous plasma. Finite-bandwidth pumps permitted the investigation of the mechanisms responsible for magnetic field generation and their control.

The interface of phase-separated ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixtures, when charged with negative ions, shows a pronounced softening of its ripplon spectrum at wave vectors around the inverse capillary length. As the electrical field perpendicular to the interface is increased beyond a value $E_c$ where the frequency of the soft ripplon vanishes, a phase transition to a spontaneous deformation of the interface in the form of an ordered array of dimples is observed.

Static low-temperature clusters above the phase transition in the H-bonded antiferroelectric squaric acid are observed by high-resolution ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR spectroscopy. Cluster formation and decay at different temperatures is observed to depend strongly on the type of impurity center inducing the cluster. Connection with the appearance of a "central peak" in light and neutron scattering is drawn.

The scaling behavior of the Landau equation of state which describes the valence transition in cerium is studied as a function of the size and valence of various chemical additives. Two major results are the relatively direct determination of the valence $N$ of cerium at the critical point (viz., $N=3.65\mathrm{}$) and the finding that the presence of chemical additives leads to a lattice-mediated rather than Coulombic bootstrapping term, which addresses the long-standing question of what is the driving mechanism for the valence transition.

The transition to a superconducting state in ultrathin (∼30 Å) granular niobium nitride is found to obey scaling laws characteristic of critical regions near phase transitions. Dynamic scaling of voltage with current is theoretically suggested in analogy with magnetic phase transitions and is experimentally demonstrated. A universal function of current and temperature involving two independent critical exponents is generated.

Surface adsorbates on clean metal surfaces are being studied by vacuum-ultraviolet differential-reflectivity methods. Results for rear gases adsorbed on metals reveal ionic characteristics of the excited configurations and weak coupling to the host electron gas.