Molecular-dynamics calculations have been used to investigate wetting phenomena on a microscopic length scale. The model systems consist of 90 water molecules on either hydrophobic and hydrophilic surfaces formed by monolayers of long-chain molecules with terminal -${\mathrm{CH}}_3$ or -OH groups. As in experiment, these two surfaces exhibit qualitatively different wetting behavior which is characterized by a microscopic analog of the contact angle.

Ionization potentials (IP’s) for Na(${\mathrm{H}}_2$O${)}_{\mathit{n}}$ and Na(${\mathrm{NH}}_3$${)}_{\mathit{n}}$ are reported for the first time up to n=20. As expected, for Na(${\mathrm{NH}}_3$${)}_{\mathit{n}}$ the IP decreases more or less monotonically with decreasing (n+1${)}^{\mathrm{-}1/3}$ to a limit consistent with the bulk value of 1.45 eV. In contrast, for Na(${\mathrm{H}}_2$O${)}_{\mathit{n}}$ we find the IP to be constant at 3.17 eV for n≥4, close to the bulk value. For comparison we solve a one-electron Schrödinger equation in a dielectrically screened Coulomb potential. While agreement with the experiment is reasonable for small n, this one-center model fails for larger clusters, thus giving some first indication for the existence of two-center localized states in these microclusters.

A sharp divergence is observed in the thermal diffusivity very close to the transition temperature of a smectic-A–smectic-C transition that is known to be at a mean-field tricritical point. Similar but less pronounced behavior near other smectic-A–smectic-C transitions reveals a relationship between the size of this anomaly and the proximity of the system to a tricritical point. An application of the Ginzburg criterion suggests that this novel behavior might indicate a crossover to an asymptotic critical regime.

We have measured the initial magnetic suppression of the B phase of the superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ at pressures from zero to 29 bars. This suppression, which is asymptotically quadratic in the field strength, is always significantly greater than the weak-coupling prediction, even at zero pressure. We also provide the first values of the A-phase specific-heat jump for pressures below the polycritical point. Microscopic models of normal liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ do not conform to these experimental constraints. Consequently, it is possible that the conventional identification of the order parameter of superfluid ${}_{}{}^3{}_{}{}^{}\mathit{A}$ is incorrect.

A parameter-free approach to phase stability in Cu-Zn substitutional alloys is shown to describe order-disorder phenomena and structural transformations with remarkable accuracy. The method is based on a multiple-scattering description of the electronic structure properties of the random alloy. Configurational order is treated within the generalized perturbation method and the concentration-functional theory. Thermodynamical properties of α and β brasses are derived from the cluster variation method. This advanced scheme is of general validity and is expected to yield similarly accurate results for other Hume-Rothery alloys.

The description of growth at vicinal surfaces leads to an anisotropic generalization of the Kardar-Parisi-Zhang equation [Phys. Rev. Lett. 56, 889 (1986)] which is investigated by a dynamical renormalization calculation. If the nonlinear terms have opposite signs parallel and perpendicular to the average step direction, the roughness is only logarithmic. This should be the case, e.g., for step-flow growth. As the temperature is lowered so that island formation on the terraces becomes significant, a sharp morphological transition to algebraic roughness is predicted.

I accurately solve the Schrödinger equation in magnetic field B for a random set of 2D point potentials. When B=0, they yield a mobility edge. When B≠0, all states are localized below a certain energy ${\mathit{E}}_{\mathit{c}}$(B). Above ${\mathit{E}}_{\mathit{c}}$(B), they are extended at the Landau energies. At other energies the localization length is a discontinuous function of B at every rational value of ${\mathit{eBd}}^2$/ch, where d is the average interpotential distance.

We use inelastic neutron scattering to establish the modulation vectors δ and correlation lengths for the incommensurate magnetic fluctuations in metallic samples of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ with x=0.075 and 0.14. In notation appropriate for a square lattice where the magnetic instability in the undoped case occurs at (π,π), the vectors δ are along (π,0) and (0,π). The correlation length ξ is larger than the distance between carriers, is weakly dependent on x, and changes significantly between 12 and 100 K for both compositions.

We show that in a highly c-oriented 2:2:1:2 Bi-Sr-Ca-Cu-O film the angular-dependent magnetic field ${\mathit{H}}^{\mathrm{*}}$ at the onset of the resistivity behaves experimentally in a way completely analogous to the critical field found in synthetic multilayered superconductors. In particular, on varying the temperature, the field ${\mathit{H}}^{\mathrm{*}}$ exhibits a crossover from a 2D to an anisotropic 3D behavior as a function of the angle ϑ between the external magnetic field and the a-b plane.

Evidence of noise-induced effects in electron-paramagnetic-resonance (EPR) experiments is reported. The first observation of a stochastic resonance phenomenon in an EPR system operating in bistable conditions has been obtained. Experimental results indicate unambiguous effects on the frequency and phase of the response of the modulated bistable system in the presence of noise. Possible new progressions in the treatment of both theoretical and experimental stochasic resonance phenomenon are perceived.

Diverse cellular systems evolve to remarkably similar stationary states. We therefore have studied and simulated a purely topological model. We use a maximum-entropy argument to predict that the average number of l-sided cells adjacent to an n-sided cell, ${\mathit{M}}_{\mathit{l}}$(n), will be linear in n. One consequence is the empirically observed linearity of the total number of edges of cells adjacent to an n-sided cell, known as the Aboav-Weaire law. The prevailing justification of that law is shown to be incorrect, and thus the apparently universal experimental slope of ∼5 remains unexplained.

We present an exact solution of a one-dimensional sandpile model for which sand is dropped along the wall and N=2 grains of sand fall over the neighboring downhill sites when the critical slope is exceeded. The slopes of N consecutive sites organize into a local state. The time evolution of the local states along the spatial direction shows a natural tree structure. As a result, various multifractals can be identified. The spatial two-point correlation function decreases exponentially with a correlation length of the order of the lattice spacing.

We prove the rigorous lower bound ${\mathit{z}}_{\exp }$≥α/ν for the dynamic critical exponent of a broad class of multilevel (or ‘‘multigrid’’) variants of the Swendsen-Wang algorithm. This proves that such algorithms do suffer from critical slowing down. We conjecture that such algorithms in fact lie in the same dynamic universality class as the stanard Swendsen-Wang algorithm.

It is shown that gravitational waves from astronomical sources have a nonlinear effect on laser interferometer detectors on Earth, an effect which has hitherto been neglected, but which is of the same order of magnitude as the linear effects. The signature of the nonlinear effect is a permanent displacement of test mases after the passage of a wave train.

We present a low-energy Lagrangian of planar QED written in terms of the local field V(x), which is the order-parameter field for the Higgs-Coulomb phase transition. In this theory, the electric charge is topological and is quantized on the classical level.$-— The relevant homotopy group is ${\mathrm{\Pi }}_1$(scrM)=scrZ, where scrM=${\mathit{scrS}}^1$ is the manifold of degenerate vacuum states in the Coulomb phase. This vacuum degeneracy is due to spontaneous breaking of a global U(1) symmetry generated by magnetic flux. The electrically charged particles are topological defects of the field V(x). The Aharonov-Bohm effect is understood without use of gauge potential and is a consequence of the extended nature of the charged particles.

Chiral properties of Wilson fermions in full QCD with two degenerate flavors at finite temperature are investigated by numerical methods. We show that when the quark mass is properly defined, for a given g (gauge coupling constant) and K (hopping parameter), its value is almost independent of whether the system is in the high-temperature phase or in the low-temperature phase. The temperature dependence of harmonic screening masses is consistent with the physical picture that both U(1) and SU(2) chiral symmetries are recovered in the high-temperature phase.

We present an extension of the singlet majoron gauge model which realizes a novel scheme of geometrical neutrino mass hierarchy proposed recently by Glashow, wherein ${\nu }_{\mathit{e}}$ and ${\nu }_{\mathrm{\mu }}$ are Majorana particles with ${\mathit{m}}_{\nu \mathit{e}}$≊${\mathit{m}}_{\nu \mathrm{\mu }}$≊${10}^{\mathrm{-}3}$ eV while ${\nu }_{\mathrm{\tau }}$ is a Dirac particle with a mass of 17 keV. Our model explains the solar-neutrino deficit via the Mikheyev-Smirnov-Wolfenstein mechanism and accounts for the recently reported anomaly in beta-decay spectra in a natural manner without any undesirable fine tuning of parameters. An interesting consequence of the model is that ${\nu }_{\mathrm{\tau }}$ is short lived with a lifetime of ≊${10}^{\mathrm{-}3–}$${10}^{\mathrm{-}1}$ sec.

An analysis of the forward-backward asymmetry in ${\mathit{Z}}^0$ decays using data from the Collider Detector at Fermilab at √s =1.8 TeV yields ${\mathit{A}}_{\mathit{F}\mathit{B}}$=[5.2±5.9(stat)±0.4(syst)]% and ${\sin }^2$θ${\mathrm{¯}}_{\mathit{W}}$ =0.${228}_{\mathrm{-}0.015}^{+0.017\mathrm{}}$(stat)±0.002(syst).

We have studied the exclusive semileptonic decay mode ${\mathit{D}}^{+}$→K${\mathrm{¯}}^0$${\mathit{e}}^{+}$${\nu }_{\mathit{e}}$ in the Fermilab photoproduction experiment E691. We find the ratio of B(${\mathit{D}}^{+}$→K${\mathrm{¯}}^0$${\mathit{e}}^{+}$${\nu }_{\mathit{e}}$)/B(${\mathit{D}}^{+}$→${\mathit{K}}^{\mathrm{-}}$${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{+}$) to be 0.66±0.09±0.14, corresponding to a ${\mathit{D}}^{+}$→K${\mathrm{¯}}^0$${\mathit{e}}^{+}$${\nu }_{\mathit{e}}$ branching ratio of 6.1±0.9±1.6)%. Combining this result with our measurement of the ${\mathit{D}}^{+}$ lifetime, we find Γ(${\mathit{D}}^{+}$→K${\mathrm{¯}}^0$${\mathit{e}}^{+}$${\nu }_{\mathit{e}}$)=(5.6±0.8±1.5)×${10}^{10}$ ${\mathrm{s}}^{\mathrm{-}1}$. We also find, using E691 averages, the ratio of decay rates Γ(D→${\mathit{K}}^{\mathrm{*}}$eν)/Γ(D→Keν) to be 0.55±0.14.

We have measured the Compton-scattering cross section on hydrogen at 60° and 135° using monochromatic tagged photons spanning the energy between 32 and 72 MeV. These data, when analyzed with a low-energy expansion of the scattering cross-section formula, provides a determination of values for the electric and magnetic polarizabilities of the proton. We find, respectively, α¯=(10.9±2.2±1.3)×${10}^{\mathrm{-}4}$ ${\mathrm{fm}}^3$ and β¯=(3.3∓2.2∓1.3)×${10}^{\mathrm{-}4}$ ${\mathrm{fm}}^3$, assuming the model-independent constraint α¯+β¯=14.2×${10}^{\mathrm{-}4}$ ${\mathrm{fm}}^3$.