Low-temperature (< 10 K) paramagnetic spectral response ${\chi }^{\prime \prime }(Q, \omega )$ in Yb${\mathrm{Al}}_3$ shows an abrupt step around ∼ 30 meV extending to ∼ 100 meV. The forward edge of the step broadens markedly and moves to lower energies with a relatively small increase in temperature (to 30 K). Disordering the Yb sublattice by dilution with Lu wipes out the inelastic step, replacing it by a broad distribution. The results give evidence of excitations across a hybridization gap in the $f$ band.

We report the first experimental results obtained by low-temperature scanning-electron microscopy on the spatial distribution of the maximum Josephson current in tunnel junctions. The experiments were performed with a nearly one-dimensional PbIn-PbBi window junction, its length being large compared to ${\lambda }_{\mathrm{J}}$. The spatial resolution is 1-2 μm and is governed by the thermal healing length. In a parallel magnetic field the different vortex states have been clearly observed. The nonlocal effects due to the beam-induced change of the phase-difference function predicted by Chang et al. have also been confirmed.

Recently it was pointed out by Shabad and Usov that in the vicinity of pulsars high-energy photons can be captured by the strong magnetic field without creating pairs. We have reconsidered this process and find that the captured "photon" is transformed into bound positronium. This positronium can be ionized by the intense electric fields present in the polar cap region, or by thermal radiation from the neutron star surface, whereby the free electrons and positrons are regained that are urgently required for the models of pulsar radio emission.

We present a new method for treating classical (or quantal) wave equations in the shortwavelength (semiclassical) regime, based on a description of the wave in the ray phase space. The coherent-state representation is defined, and the equation which it obeys is given and solved under assumptions similar to those of conventional eikonal theory. As indicated by an example, the result is a smooth distribution on phase space which, when "projected" onto configuration space, yields a wave field with no caustic singularities.

We suggest that the $\rho$ meson is a dynamical gauge boson of a hidden local symmetry in the non-linear chiral Lagrangian. The origin of the $\rho$-meson mass is understood as the Higgs mechanism of the hidden local symmetry. The low-energy dynamics of $\rho$, $\pi$, and matter fields, including the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin relation and $\rho$-coupling universality, is consistently described in this new framework. The electromagnetic interaction can be introduced in a unique manner, which gives a successful explanation of $\rho$ dominance of the photon coupling.

We show that the chiral Schwinger model, which is anomalous, yields a consistent and unitary, although not gauge-invariant, theory. The model is exactly solvable and contains a free massive vector boson plus harmonic excitations.

I present a systematic method for the development of the effective-action expansion in perturbation theory. The multiderivative terms beyond the effective potential can be evaluated in a direct and simple manner relying only on the familiar momentum space and Feynman propagator. I have used the self-coupled scalar field to explain the details of this new formulation. The effective-action expansion for this model in the one-loop approximation is evaluated up to the terms containing four derivatives. This method can be readily generalized to other models with spins and internal symmetries.

We examine the feasibility of identifying in a hadron machine the standard, neutral Higgs boson, produced in association with a $W$, when the mass of the Higgs is between approximately 100 GeV and $2m_W$. The production cross section is calculated with quasirealistic cuts imposed under the assumption that the Higgs decays into $t\overline{t}$. Possible backgrounds arising from the continuum production of $t\overline{t}$, $t\overline{b}$, or $\overline{t}b$ accompanied by a $W$ are computed as well.

The observed differential cross section for the process ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}({\pi }^{+}, {\pi }^{-}){}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ at 50 MeV is successfully reproduced in the framework of multiple-scattering theory, with medium effects on $\pi$ and $\Delta$ propagation fitted to elastic $\pi$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ scattering.

Deep-inelastic inclusive electron-scattering cross sections from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ have been measured at 60°, 90°, and 140° and at energy transfers including the $\Delta (3, 3)$ region. The transverse response function in the momentum interval 300 MeV/c <|q| < 600 MeV/c was extracted by the Rosenbluth prescription. Different theoretical approaches to the quasielastic region are compared to the data. A mass-number scaling is observed.

The observation of $\Lambda$-hypernuclear levels in ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}$ by associated production through the (${\pi }^{+}, K^{+}$) reaction is reported. The ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}$ excitation-energy spectra were recorded at laboratory scattering angles of 5.6°, 10.3°, and 15.2°. They show two major peaks—one attributed to the ground state, and one about 11 MeV higher. These results are compared to the strangeness-exchanging ($K^{-}, {\pi }^{-}$) reaction. The measured cross sections are compared to relativistic distorted-wave Born-approximation calculations.

It is shown that in electron spin-echo spectroscopy the entire echo modulation, normally measured point by point in a sequence of experiments, can be obtained by a single experiment with extended-time excitation by use of a coherent, a stochastic, or a pulse-burst stimulation followed by a strong refocusing pulse.

The new principle of radiation-pressure trapping of neutral dielectric particles by means of alternating light beams was demonstrated in an optical levitation experiment. Stable trapping of micron-sized spheres was observed due to alternating scattering-force fields under conditions where stable cw trapping was not possible. Application of this principle to neutral-atom trapping as a means of circumvention of the optical Earnshaw theorem is suggested. A new stable cw optical trap for spheres was also discovered.

We show that circular dichroism exists in the photoelectron angular distributions from oriented linear molecules in the electric dipole approximation. Contributions to the dichroism arise solely from interferences between degenerate photoelectron continua with $m$ values differing by ±1. We identify specific photon-propagation, electron-detection configurations where circular dichroism will be observable. Finally, we illustrate the magnitude of this effect through ab initio calculations for photoionization out of the $4\sigma$ orbital of an oriented CO molecule.

Global or discrete Alfvén waves have been investigated with a full nonlinear, three-dimensional, ideal magnetohydrodynamic simulation code. When driven strongly with an outside antenna, those modes grow to a very high level, $\frac{\delta B}{B_T}\simeq 10\%$. No destabilization of the plasma is observed. These modes appear to be much more efficient than the ones in the continuum in absorbing the pump energy.

Surface extended-x-ray-absorption fine-structure measurements reveal that formate (HC${\mathrm{O}}_2$) groups on Cu(100) chemisorb via the two oxygen atoms in adjacent fourfold hollow sites with an average O-Cu nearest-neighbor bond length of 2.38±0.03 Å. This distance is significantly (∼0.4 Å) longer than typical O-Cu bonds in bulk compounds and all known surface complexes. The unusually large O-Cu distance is attributed to a steric effect involving the C atom in HC${\mathrm{O}}_2$ and the nearest-neighbor Cu surface atoms.

Small single crystals of ${\mathrm{Nb}}_3$Sn were grown and used to study the lattice dynamics by means of inelastic neutron scattering. Almost complete sets of phonon dispersion curves could be obtained for the main symmetry directions. The results are generally in very good agreement with the predictions of Weber based on the nonorthogonal-tight-binding method. In particular it has been confirmed that the (111) LA branch exhibits a pronounced anomaly.

The kinetics of an order-disorder transition is studied by Monte Carlo renormalization-group methods. The block-spin transformation acts to renormalize both the growing domains and the moving interfaces separating them. After several iterations, the growth is found to be self-similar under a simultaneous rescaling of space and time. The growth law for the average size of domains is then determined by a matching condition. Good agreement with the results of previous studies is obtained.

The breakdown of hydrodynamics predicted by Mazenko, Ramaswamy, and Toner is verified by experiments which use the excitation of second-sound resonances in the smetic-$A$ phase of octylcyanobiphenyl. One finds a diverging viscosity $\Delta \tilde{\eta }\cong \frac{(5\mathrm{}\times {10}^6\mathrm{P} \mathrm{s})}{\omega }$, which has an order of magnitude comparable with the crude predictions of the theory.

We have measured the in-plane x-ray diffraction pattern of the two-component ${\mathrm{K}}^{+}$ -N${\mathrm{H}}_3$ liquid layers in the ternary graphite intercalation compound K${\left(\mathrm{N}{\mathrm{H}}_3\right)}_{4.33}$${\mathrm{C}}_{24}$. The measured pattern is in semiquantitative agreement with the scattering calculated for a random distribution of coplanar hard ${\mathrm{K}}^{+}$ and N${\mathrm{H}}_3$ disks, provided that the ${\mathrm{K}}^{+}$ ions are bound symmetrically to four N${\mathrm{H}}_3$ molecules. We show that the K-N${\mathrm{H}}_3$ layers constitute the two-dimensional structural analog of the well-known bulk three-dimensional K-N${\mathrm{H}}_3$ metal-ammonia solutions.