The $4f$ spectral density of the Falicov-Kimball model is calculated within the "resonance broadening" approximation. This allows a qualitative interpretation of the double-peak structure observed in $4f$-derived photoemission for the light-rare-earth systems: A partial delocalization of the $f$ electrons into the $d$ band is deduced in the $\gamma -\alpha$ transition for Ce; the two peaks move away from the Fermi energy with the $f$ level as one goes from Ce to Pr to Nd. The only feature obtained in Sm-based systems can be understood within the same picture.

We develop for the first time an approach à la Borland to Anderson localization in multidimensional systems; it provides a proof of localization when the Green's function decays exponentially, e.g., at large disorder or large energy. This approach also provides results about the Lyapunov exponents associated with a quasi-one-dimensional system. Finally we obtain the result that the singular continuous spectrum, found in some incommensurate systems, turns into exponential localization under arbitrarily small local perturbations.

A single-determinant experimental Be hybrid-atom wave function is obtained by the quantum formalism of Clinton and Massa, from Larsen and Hansen's single-crystal x-ray diffraction data. Physical properties calculable from this wave function are unobtainable from current methods of diffraction analysis. The least-squares fit using all experimental data gives an $R$ factor of 0.0018, and quantitatively describes charge redistribution due to crystal bonding in agreement with ab initio calculations.

A minimum in the electrical resistivity as a function of temperature was recently observed in pure thin potassium wires near 1 K. We interpret this effect in terms of inelastic-scattering events interrupting the coherence of one-dimensional localized electrons. Assuming that a minimum energy transfer is required for a collision to be effective, we find that either electron-electron scattering or electron-phason scattering could be the appropriate inelastic mechanism.

Small-angle Rayleigh-scattering experiments have been performed in liquid carbon tetrachloride subjected to a temperature gradient. The contributions of both the heat mode as well as the viscous mode to the enhanced scattering intensity are observed. Although the observations are qualitatively in agreement with theoretical predictions, the viscous contribution is much larger than predicted.

We introduce a coarse-grained molecular dynamics method. This approach is suitable for the numerical simulation of the evolution of large ensembles of interacting particles over macroscopic time scales. We report an application of the method to nonequilibrium chemically reactive systems. We obtain the nonequilibrium distributions of the reactants during the reaction which exhibits nonlinear behavior.

For field equations of Hamiltonian form the relation between constants of motion and solutions of the linearized equation is discussed. A known result is that the Poisson bracket of a constant of motion with the field variable solves the linearized equation. Here the following converse result is obtained: If a δu which satisfies the linear equation is of the form δu=[u,T], then T is a constant of motion. Further, ∂T/∂t is also a constant. The sequence [T,∂T/∂t], [[T,∂T/∂t],T],. . . is shown to produce other nontrivial constants.

Randomness and chaos in physical systems are usually ultimately attributed to external noise. But it is argued here that even without such random input, the intrinsic behavior of many nonlinear systems can be computationally so complicated as to seem random in all practical experiments. This effect is suggested as the basic origin of such phenomena as fluid turbulence.

It is shown that (i) the N-component Ashkin-Teller model in d=2 has continuous O(N) symmetry, (ii) its critical properties near the decoupled Ising transition are determined by the massive Gross-Neveu [(ψ¯ψ${)}^2$] model in general and the (integrable) massless version along a line, (iii) the known results for the massless Gross-Neveu model imply that the first-order transition found as N→∞ persists down to N=3 along this line, (iv) the supersymmetry of the N=3 model implies that the leading singularity of the free energy is zero along the first-order line, and (v) the N=4 model along this line decouples into two identical N=2 models up to subleading corrections.

We present new data on the A dependence of the inclusive production of high–transverse-momentum hadrons, both singles and symmetric pairs. These data qualitatively support the hypothesis that the observed A dependence results from multiple scattering of quarks and gluons within the target nucleus.

Experimentally observed sharp lines in the positron-emission spectra resulting from low-energy heavy-ion collisions are interpreted in terms of the production and subsequent decay of a neutral, pseudoscalar particle. This particle has a mass of about 1.6 MeV and a lifetime of about 1.3×${10}^{\mathrm{-}13}$ sec.

A search has been performed for the lepton-flavor-nonconserving reaction ${\mu }^{\mathrm{-}}$+Ti→$e^{\mathrm{-}}$+Ti using a time-projection chamber. No candidate events were observed, resulting in a limit of Γ(${\mu }^{\mathrm{-}}$+Ti→$e^{\mathrm{-}}$+Ti) / Γ(${\mu }^{\mathrm{-}}$+Ti→capture) <1.6×${10}^{\mathrm{-}11}$ (90% C.L.) for this reaction relative to ordinary muon capture.

The production of supersymmetric particles in ultrahigh-energy cosmic-ray interactions in the atmosphere is investigated. We find that the pair production and subsequent decay of a light (∼3–5 GeV) gluino can lead to fluxes of neutral, weakly interacting superparticles which can be comparable to neutrino fluxes. Relevant processes for detecting photinos or scalar neutrinos in large neutrino detectors are discussed and several reactions with cross sections as large as those of ordinary ν interactions are examined.

Besides hadrons and eight electroweak gauge bosons, topological particle theory predicts four generations isodoublet Dirac leptons (e,μ,τ,λ plus neutrinos) and eight generation-changing neutral scalar bosons $H_{\lambda \tau }$, $H_{\lambda \mu }$, $H_{\tau e}$, $H_{\mu e}$, and conjugates. Seven vector bosons, all H’s and λ acquire masses≫1 GeV from direct couplings to heavy elementary hadrons with masses ≳1 TeV. We estimate that $m_{\lambda }$≲1 TeV. H-mediated radiative corrections give masses to μ and τ in first order, to e in second order. Lepton-generation numbers are absolutely conserved and neutrinos acquire small masses but do not mix.

We perform exact numerical calculations of interactions between pairs and chains of skyrmions, and make estimates of many-body forces. The picture of skyrmion interactions that emerges is very different from the one based on the product Ansatz for the chiral field employed in previous studies.

Electric ground-state properties of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ have been measured in a consistent way by observation of the Coulomb interaction of aligned ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ ions with heavy target nuclei. Besides the quadrupole moment ($Q_s$=-3.70±0.08 $e^2$ ${\mathrm{fm}}^2$) and the B(E2,${\mathrm{}(3/2)\mathrm{}}^{\mathrm{-}}$→${\mathrm{}(1/2)\mathrm{}}^{\mathrm{-}}$) value (8.3±0.5 $e^2$ ${\mathrm{fm}}^4$), the tensor moments of the nuclear polarizability ${\tau }_{12}$ and ${\tau }_{11}$ were determined (${\tau }_{12}$=${\tau }_{11}$=0.23±0.06 ${\mathrm{fm}}^3$). Present theoretical investigations on the structure of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ reveal difficulties in providing a unified description of all four properties.

We report the first experimental measurements for the energy level of a metastable state of ${\mathrm{Be}}^{\mathrm{-}}$. The ions were produced in sequential charge-exchange collisions between 50- to 60-keV ${\mathrm{Be}}^{+}$ ions and lithium vapor. The center-of-mass energy of autodetaching electrons was found to be 2.53±0.09 eV. This result is in good agreement with previously calculated values for the ${\mathrm{Be}}^{\mathrm{-}}$(1${\mathrm{s}}^2$2s2${\mathrm{p}}^2$${)\mathrm{}}^4$P state energy.

The first measurements of total cross sections for positrons (5–49 eV) colliding with a non-room-temperature gas (namely potassium) are reported. Comparisons of these measurements with the corresponding electron measurements using the same apparatus and technique (a beam-transmission method) indicate an overall degree of similarity that has not been observed for any other target atoms or molecules, which could be related to the large polarizability of potassium atoms.

We present measurements of the dynamic behavior of macroscopic structures observed in a periodically excited air jet. The transitional weakly turbulent state is shown to be characterized by a strange attractor with low dimensionality (ν=2.6), whereas motion of the turbulent flow is not restricted to a low-dimensional attractor.

Rayleigh-Bénard convection is studied in alcohol-water mixtures in which the diffusion of concentration opposes convection via the Soret effect. Near onset, the convective rolls are found to move continuously as traveling waves, in contrast to the stationary roll patterns observed in homogeneous fluids. Dependent upon the temperature difference across the fluid layer (i.e., Rayleigh number), these traveling-wave states are either periodic or chaotic. At larger Rayleigh numbers, time-independent flow is observed which is the same as that expected for the homogeneous fluid mixture.