New data on the polarization observables $i{T}_{11}$, $T_{20}$, $T_{21}$, and $T_{22}$, supplemented by $\frac{d\sigma }{d\Omega }$ and information from reasonable theoretical models, are used to extract the pion-deuteron scattering amplitude at 256 and 294 MeV. Using these amplitudes, partial-wave components are calculated and the spin-transfer parameter $i\left(11\right|20)$ is predicted. Some observations on helicity phase patterns are also made.

Effects of final-state interactions on the nuclear structure functions of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ are calculated. In kinematics similar to regions experimentally explored for some light nuclei, the transverse and longitudinal structure functions are almost equally modified by final-state effects. However, decreasing the relative energy between the nucleon and the residual nucleus leads to a significant enhancement of the transverse-to-longitudinal strength ratio.

The magnetic form factor of ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ has been measured by elastic electron scattering in the momentum-transfer range between 1.8 and 3.3 ${\mathrm{fm}}^{-1\mathrm{}}$. The $1f_{\frac{7}{2}}$-neutron-orbit radius inferred from these data definitely demonstrates that the explanation of the Coulomb-energy anomaly cannot be found in a reduction of the valence-orbit radius.

We show that SO(3) gauge potentials arise in the Born-Oppenheimer description of the interaction between the dipole and quadrupole vibrations in even-even spherical nuclei and derive the effective Hamiltonian for the quadrupole motion.

Fluctuation properties of positive-parity states in ${}_{}{}^{26}{}_{}{}^{}\mathrm{Al}$ from the ground state to the resonance region (0-8 MeV excitation energy) are found to be consistent with the Gaussian-orthogonal-ensemble version of random-matrix theory. Although isospin is an approximately good quantum number in this system, the fluctuation properties of the combined sequence ($T=0\mathrm{}$ and $T=1\mathrm{}$ states) are consistent with those of a single Gaussian-orthogonal-ensemble sequence. This agrees with earlier predictions by Dyson and Pandey and with recent analysis by Guhr and Weidenmüller.

An interatomic potential is developed for beryllium based on the simultaneous fit to the total energy of 2- to 5-atom clusters obtained in the local-spin-density approximation. The increasing $s-p$ hybridization with cluster size is incorporated through a three-body term depending on the number of atoms. Results using the potential give an excellent description of the early stages of crystal growth and a correct prediction of the stability of the hcp lattice over bcc and fcc phases.

A novel and relatively simple technique based upon the line absorption method to measure relative transition probabilities is reported. The absorption measurements are performed with the use of a single hollow cathode discharge lamp, which serves as a light source as well as an absorption cell. The technique has been applied to measure the relative transition probabilities of a few ground-state transitions in UI. This technique can also lead to the determination of excitation temperature in the discharge without the aid of data from other sources.

A linearly polarized tunable cw dye laser was used to excite ${\mathrm{K}}_2$ from the ground $X{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{+}$ state into the continuum of the $B{}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{u}}^{}{}_{}{}^{}$ state. Resulting photodissociation produces excited atomic $\mathrm{K}\left({}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}\right)$ which radiates on the $D_2$ line. As the laser is tuned through the molecular bound-free absorption profile, we have observed a large variation in the polarization of atomic fluorescence ranging from plus 15% ± 2% to minus 6.3% ± 0.4%. We believe this variation can be explained in terms of molecular rotation during dissociation. These results are consistent with a completely adiabatic model for the dissociation.

Magnetic resonance imaging is used to study oil and water invasion in a model porous medium. Images taken normal to the flow direction are processed to give both the oil saturation and the fractal character of the oil distribution. These images reveal qualitative differences between the cases of invasion by the wetting (water) and nonwetting (oil) fluids. We have also found large saturation fluctuations in the residual oil state in which the oil consists entirely of disconnected blobs.

We present results of Monte Carlo simulations of kinetics of spinodal ordering on a one-dimensional Ising chain with competing interactions up to third neighbors for Glauber and Kawasaki dynamics. Application of these results to the $2H-6H$ transformation in SiC shows that the arrested state of the transformation possesses long-range order but lacks short-range correlations.

We have used a surface-plasmon-resonance technique to probe Xe multilayer-film growth dynamics on vapor-deposited Ag(111) from 67 to 85 K. At low temperature, more than 10 statistical layers are observed, but above 75 K, films complete only about 2 layers before nucleating islands. We discuss activation energies, long-term instabilities, and annealing trends, and show that the island nucleation correlates with underlying features of the substrate.

Using a cluster description of a coherent binary alloy, we predict and contrast bulk and epitaxial composition-temperature phase diagrams. For alloys with stable ordered compounds in bulk, epitaxial growth away from the lattice-matched composition distorts phase boundaries and changes ordering temperatures. For alloys insoluble in bulk below a miscibility-gap temperature $T_{\mathrm{MG}}$, the epitaxial alloy may remain stable to temperatures > 1200 K below $T_{\mathrm{MG}}$ even on lattice-matched substrates, with stoichiometric compounds possible at low temperature.

We calculate the total energy of random ${\mathrm{Al}}_{0.5}{\mathrm{Ga}}_{0.5}\mathrm{As}$ alloys and ordered ${\left(\mathrm{AlAs}\right)}_n{\left(\mathrm{GaAs}\right)}_n$ superlattices through a series expansion in multi-atom interaction energies obtained from the local-density formalism. We find that the alloy is more stable than the monolayer ($n=1\mathrm{}$) superlattice at all temperatures, but it could order into longer-period ($n\ge 2$) superlattices below a critical temperature $T(n,\mathbf{G})$ calculated for various growth orientations $\mathbf{G}$.

A calculation of the magnetic (001) surface structure of an antiferromagnetic insulator with the MnO spin arrangement is reported. The calculation is based on classical spins with Heisenberg interactions which are (a) between second neighbors throughout the bulk and surface, (b) between nearest-neighbor spins at the surface layer, and (c) between nearest-neighbor spins in the first and second layers. It is found that for a range of exchange parameters, incommensurable ground-state structures are obtained.

We compare the high perceptual efficiency exhibited by humans at a number of tasks in visual perception with that predicted by models of visual information processing, in particular the broad class of "feature detector" models, which we represent as an Ising spin system responding to a quasirandom magnetic field. The observed excitatory-center, inhibitory-surround organization of the neural receptive fields is seen to be desirable.

We discuss topological invariants for Fermi systems that have time-reversal invariance. The TK${\mathrm{N}}^2$ integers (first Chern numbers) are replaced by second Chern numbers, and Berry's phase becomes a unit quaternion, or equivalently an element of SU(2). The canonical example playing much the same role as spin ½ in a magnetic field is spin ½ in a quadrupole electric field. In particular, the associated bundles are nontrivial and have ± 1 second Chern number. The connection that governs the adiabatic evolution coincides with the symmetric SU(2) Yang-Mills instanton.

We discuss the problem of solving large linear systems of equations that arise in lattice systems with disorder. Three examples of this kind of problem are (i) computing currents in a random-resistor network, (ii) computing the fermion (quark) propagator in lattice quantum chromodynamics, and (iii) the discrete Schrödinger operator with a random potential (the Anderson model of localization). We show that the algebraic multigrid is a very effective way to compute currents in a random-resistor network. It is likely that similar techniques will apply to the other problems.

Statistical mechanics of gravitational fields describing the black-hole topological sector, and the correspondence to thermodynamics, are considered. The Euclidean action is evaluated on the constraint hypersurface and a measure is obtained, resulting in a path-integral form of the canonical partition function. We obtain the usual black-hole entropy plus quantum corrections when the temperature and size of the system are appropriate. Under other conditions, we give evidence for the existence of a phase transition (change of topology).

We present the results of an experiment, carried out using a beam balance, designed to search for a short-range, isospin-coupling component of the fifth force. The value for the coupling constant $\xi$ was found to be (0.8 ± 2.0) × ${10}^{-2\mathrm{}}$. The significance of this result is discussed with reference to other recently published work.

Quasielastic meson-baryon scattering is reformulated in $t$-channel language (meson exchange) instead of $s$-channel language (baryon-resonance formation), by use of skyrmion methods. A new selection rule emerges, valid to leading order in large $N_c$. The isospin of the exchanged state must equal its total angular momentum (spin+orbital). Differences between the two-flavor and the three-flavor approach are discussed.