Generalizing a construction of Berry and Simon, we show that non-Abelian gauge fields arise in the adiabatic development of simple quantum mechanical systems. Characteristics of the gauge fields are related to energy splittings, which may be observable in real systems. Similar phenomena are found for suitable classical systems.

The absence of chiral symmetry breaking for sufficiently high temperature (or chemical potential) is rigorously demonstrated in SU(2) lattice gauge theories with massless fermions in any number of dimensions.

The properties of certain recently proposed topological vortices which can occur at either grand-unification or intermediate energy scales are examined. These vortices are topologically stable in that they survive any subsequent symmetry breakings. We find them also to be dynamically stable because some of their quantum numbers have fractional values. Zero-energy bound states with certain fermions are found and these states are seen to transform like SU(5) families and mirror families. We also comment on the analog of the Rubakov-Callan effect for the above vortices.

A recent isobar-model, partial-wave analysis of $\pi N\to \pi \pi N$ finds strong indications of the $F_{35}$ pion-nucleon resonance belonging to the (70,$L=2^{+}$) baryon multiplet. This conclusion is drawn from recent predictions of baryon decays obtained with baryon compositions determined by the Isgur-Karl quark model. The highly inelastic $F_{35}$ resonance is observed through its dominant $p$-wave decay to $\rho N$.

In a study of 2.7 million $\frac{J}{\psi }$ decays with the Mark III, a new magnetic detector at SPEAR, we have observed the sequential decay $\frac{J}{\psi }\to \gamma {\eta }_c$, ${\eta }_c\to \phi \phi$. The product branching fraction is (1.02±0.25±0.14)×${10}^{-4\mathrm{}}$, where the quoted errors are statistical and systematic, respectively. Analysis of the final-state angular distributions provides the first experimental determination that the spin and parity of the ${\eta }_c$ are $0^{-}$.

Deep-inelastic electron scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ has been measured at 60°, 90°, and 140° and at inelasticities up to and including the $\Delta (3,3)$ region. Longitudinal response functions in the momentum interval $300 \mathrm{MeV}/c<\left|\overrightarrow{\mathrm{q}}\right|<\mathrm{}600\mathrm{} \mathrm{MeV}/c$ were extracted. The experimental Coulomb sum rule is observed between the two calcium isotopes.

We present the energies, widths, and cross sections of the isovector monopole resonance in nuclei between ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ excited by the (${\pi }^{\pm }$, ${\pi }^0$) reactions. We also give results for the giant dipole resonance. Both resonances exhaust the same substantial fraction of the cross section calculated in a random-phase, distorted-wave impulse-approximation model. No isovector quadrupole resonance was observed.

The influence of the energy of the incident photon on the statellite structure associated with ionization in the outer $s$ shell of the heavier rare gases is calculated. When the photon energy decreases from 200 to 50 eV, an increase in satellite intensity of about 30% is predicted for Ar. This prediction agrees, within the experimental accuracy, with recent observations. Similar behavior is predicted for Kr and Xe.

Mass spectra are presented for sodium clusters of $N$ atoms per cluster ($N=4-100\mathrm{}$) produced in a supersonic expansion with argon carrier gas. The spectra show large peaks or steps at $N=8, 20, 40, 58, \mathrm{and} 92$. These can be understood in terms of a one-electron shell model in which independent delocalized atomic $3s$ electrons are bound in a spherically symmetric potential well.

A plasma current is initiated and raised to a quasistationary level of about 20 kA by injection of the lower hybrid wave into a cold and low-density plasma produced by electron cyclotron resonance. The plasma current rises more slowly than the experimentally obtained $\frac{L_p}{R_p}$ magnetic diffusion time of the bulk plasma. The current rise time is inversely proportional to the bulk electron density, and agrees well with the collision time of the current-carrying high-energy electrons with the bulk plasma.

The nonlinear interaction of externally excited convective cells was investigated experimentally. Two cells of the same polarity were observed to coalesce into one large cell provided their relative distance was sufficiently short. The nonlinear nature of the interaction was explicitly demonstrated. Two cells of opposite polarity interact through a mutual perturbation of orbits.

Ionospheric heating is studied by numerical solution of the modified Zakharov equations for typical ionospheric heating parameters. It is shown that modulational instability followed by soliton formation can be more important than the previously considered parametric decay instability.

An important unsettled question exists whether high-frequency (gigahertz to terahertz) acoustic phonons undergo specular or diffuse scattering from a crystal boundary. In this Letter, we demonstrate a phonon-imaging method which clearly differentiates between these two processes. For optically polished sapphire (${\mathrm{Al}}_2$${\mathrm{O}}_3$) at 1.6 K, we observe sharp singularity patterns which are unambiguously identified with specular reflection. For a degraded surface, a broad spatial pattern associated with diffuse scattering is observed. A theoretical basis for phonon reflection imaging is presented.

Long-ranged density correlations, varying on the scale of the capillary length $L_c$, exist in the liquid-vapor interface in a weak gravitational field. A scaling hypothesis, similar to that made near the bulk critical point, predicts that in dimensions $d<\mathrm{}3\mathrm{}$, the interface width $W\to \infty$ as $L_c\to \infty$. For $d>\mathrm{}3\mathrm{}$, $W$ can remain finite provided there is power-law decay of correlations for separations less than $L_c$. These results are consistent with capillary-wave theory.

We advance an experimental method for the characterization of the geometric site distribution of a fractal structure, which rests on the interrogation of direct, long-range, singlet-singlet, intermolecular, electronic energy transfer. Time-resolved picosecond spectroscopy was utilized to study energy transfer from rhodamine B to malachite green doped into a porous glass, resulting in a fractal dimension of $\overline{d}=1.74\mathrm{}\pm 0.12$ for this irregular structure.

A model Hamiltonian is introduced for an impurity in a filled-band host, where the intraatomic electron interaction $U$ on the impurity site is included. The Auger spectrum ending in two holes in the valence band ($\mathrm{VV}$) is solved exactly for the impurity. For a certain range of values of $U$ there is besides the normal Cini-Sawatzky quasiatomic peak a new discrete twohole state at much lower binding energy. This solution is used to explain the strong anomaly of the Pd $M_{4,5}\mathrm{VV}$ spectrum in $\mathrm{Ag}\mathrm{Pd}$ alloys.

By means of angle-resolved photoemission, the unoccupied band structure of Be along the $\Delta$ axis has been determined. While the data are in generally good agreement with the results of a self-consistent pseudopotential calculation, additional structure near the threshold for plasmon production is seen. It is argued that this structure is a many-body distortion caused by the electron-plasmon interaction.

Photoemission studies of $\mathrm{RE}{\mathrm{Ru}}_2$ and $\mathrm{RE}{\mathrm{Pd}}_2$ ($RE=\mathrm{C}\mathrm{e},\mathrm{P}\mathrm{r},\mathrm{N}\mathrm{d}$) reveal two $4f$-derived features with an energy separation of ∼2.5 eV, which move in parallel to larger binding energies in going from Ce to Pr to Nd. These results, which are at variance with predictions of Anderson-model treatments based on the large-orbital-degeneracy approximation, are compatible with the treatments of Liu and Ho and of Riseborough, who distinguished between the two peaks on the basis of their screening geometries.

Energy distribution curves from La and Pr were taken from 32 to 80 eV photon energies. Above 50 eV the valence-band photoemission in La is very weak, implying that previous studies of Ce have underemphasized the $4f$ contributions. Pr exhibits two peaks attributable to $4f$ electrons, similar to the structures in Ce.

The angular and energy distributions of ${\mathrm{K}}^{+}$ ions scattered at normal incidence with an initial energy of 35 eV on a W(110) surface were measured for various crystal orientations. The complex distributions show rainbows which are due both to extrema in the deflection functions for the two scattering angles as well as to an extremum in the final energy as a function of the impact parameter. With use of computer simulations with a nonadditive model potential all observed structures can be explained.