While ideal fluid membranes are characterized solely by curvature elasticity, many structural (‘‘external’’) properties of real membranes are strongly influenced by internal degrees of freedom. Here, we consider, within mean-field theory, the effect of in-plane vector order (such as the molecular tilt in surfactant bilayers) on the shapes of closed vesicles with the topology of a sphere. We find that coupling between in-plane order and Gaussian curvature causes continuous shape changes from spherical to cylindrical vesicles as the degree of in-plane order increases.

From a new mathematical identity and by using the fractional difference between the momentum of a roton and the momentum at the bottom of the roton minimum as a small expansion parameter, a first-order perturbation treatment of the roton-vortex interaction is developed. The resulting analytic expressions for the distribution of transverse momentum transfer, in terms of elliptic integrals, are shown to be in excellent agreement with recent computer-simulation results of Samuels and Donnelly and are convenient for computing the total momentum transfer.

New wetting and nonwetting phenomena for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ adsorbed on weak-binding substrates such as the alkali metals are predicted. With a nonlocal density-functional model, we calculate the density profile of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films adsorbed on surfaces characterized by an attractive van der Waals potential tail of strength ${\mathit{C}}_3$ and a well depth D. As a function of ${\mathit{C}}_3$ and D, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films exhibit both nonwetting and wetting, the latter being accompanied by a prewetting transition. Specifically, we find that ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ will not wet all the alkali metals; only on Li and Na is wetting behavior, with prewetting, expected.

A new method for simulating nonadiabatic quantum processes is presented. It is suitable for transitions which are not dominated by near crossing of potential surfaces. The method is applied to the calculation of the radiationless transition rate of the hydrated electron from its lowest excited level to the ground state. The results are consistent with recent experimental indications that this process dominates the solvation dynamics of the electron in water.

The shake-up and shake-off spectrum for ${\mathrm{N}}_2$ adsorbed on Ni(100) has been recorded up to 75 eV above the 1s lines. Using photoelectron-diffraction effects, the complete satellite spectra from the two inequivalent nitrogen atoms have been separated. The two spectra are significantly different which gives information about the character of the shake-up states. The proposed interpretation is further supported by a comparison with the C-1s shake-up spectrum for adsorbed CO. More than 80% of the spectral strength is contained in the satellites.

Edge magnetoplasma excitations in a two-dimensional electron system have been studied in radio-frequency experiments which exhibit a strong nonlocal behavior of the plasmon dispersion. The nonlocality is shown to be caused by the diagonal conductivity ${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}$, which, via a length l∝${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}$, governs the spatial distribution of the plasma charge oscillations in the direction perpendicular to the plasmon wave vector, i.e., to the edge of the two-dimensional layer.

We have observed an ultrarapid electronic phase transformation to a centrosymmetric electronic state during laser excitation of GaAs with intense femtosecond pulses. Reflection second-harmonic intensity from the upper 90 atomic layers vanishes within 100 fs; reflectivity rises within 0.5 ps to a steady value characteristic of a metallic molten phase, long before phonon emission can heat the lattice to the melting temperature.

Six new phase diagrams, including a novel multicritical topology and two new ordered phases, high-entropy ferrimagnetic and antiquadrupolar, are found in the spin-1 Ising model with only nearest-neighbor interactions, for negative biquadratic couplings. Thus, the global phase diagram of this simple spin system includes nine distinct topologies and three ordered phases. It is indicated that these results, obtained by mean-field theory, are applicable to three-dimensional systems.

We performed density-functional-theory total-energy and force calculations of clean and Na-covered GaAs(110) for two coverages: Θ=1/2 (one Na atom per pair of Ga and As) and Θ=1/4. The atomic positions of the adsorbate and of the top three substrate layers are fully relaxed. We discuss the nature of the adsorbate-substrate interaction, the adsorbate-adsorbate interaction, how the adsorbate modifies the clean-surface geometry, and how the atomic and electronic structures are correlated. It is found that the adsorption is partially ionic. The highest occupied adsorbate-induced ‘‘band’’ reflects the properties of a Mott-insulator state, where the lowest unoccupied state is a one-dimensional Bloch state.

A qualitative and quantitative description (exact diagonalization of finite clusters) of the doping dependence of one-electron-removal and -addition spectral weights is given. A half-filled Hubbard system in the localized limit has two low-energy electron-addition (removal) states for each hole (electron) created by doping. In contrast, a charge-transfer system in the localized limit is fundamentally asymmetric between hole and electron doping. However, when the hybridization is increased this asymmetry disappears quickly and both holes and electrons introduced by doping show a strongly correlated behavior.

By means of Monte Carlo simulations and Coulomb-gas scaling it is shown that the vortex fluctuations in the three-dimensional anisotropic XY model become effectively two dimensional just above the critical temperature. This suggests that the resistance scaling function in the case of high-${\mathit{T}}_{\mathit{c}}$ superconductors should be identical to the one for conventional superconducting films. Some experimental evidence for this is pointed out.

We present analytic and numerical studies of rupture propagation in a one-dimensional model of an earthquake fault. In the case of a fault that is uniformly at its slipping threshold, the propagation speed is determined by a dynamic selection mechanism elsewhere identified as ‘‘marginal stability.’’ At any nonzero distance below threshold, however, a solvability principle appears to be applicable. We describe the way in which these two mechanisms turn out to be consistent with each other and comment upon the unusual role of the short-wavelength cutoff.

The effects of Gaussian quasimonochromatic (narrow band) noise have been investigated with an analog electronic circuit model. The escape probability and the reciprocal mean time to reach the top of a potential barrier were found to differ exponentially strongly. An extremely steep statistical distribution was observed and is discussed. For systems fluctuating in a symmetric single-well potential the distribution was found to be independent of the shape of the potential.

The concept of ‘‘fractional statistics’’ is reformulated as a generalization of the Pauli exclusion principle, and a definition independent of the dimension of space is obtained. When applied to the vortexlike quasiparticles of the fractional quantum Hall effect, it gives the same result as that based on the braid-group. It is also used to classify spinons in gapless spin-1/2 antiferromagnetic chains as semions. An extensive one-particle Hilbert-space dimension is essential, limiting fractional statistics of this type to topological excitations confined to the interior of condensed matter. The new definition does not apply to ‘‘anyon gas’’ models as currently formulated: A possible resolution of this difficulty is proposed.

Completing Ginibre’s work we determine the joint probability density of eigenvalues in a Gaussian ensemble of real asymmetric matrices, which is invariant under orthogonal transformations. The symmetry parameter τ may vary from -1 (antisymmetric ensemble) through 0 (completely asymmetric ensemble) to +1 (symmetric ensemble). The elliptic law for the average density of eigenvalues in the limit of large dimension is recovered. Matrices of the type considered appear in models for neural-network dynamics and dissipative quantum dynamics.

The basins of attraction of period-2 attractors can be subdivided into two domains, one for each of the stable trajectories which are one drive cycle apart. This generalizes to period-n attractors. Periodic drive signals can be replaced by certain chaotic signals which results in the elimination of multiple domains of attraction. The attractors are similar to the original ones, but two systems on the same attractor cannot get out of phase with each other.

Necessary and sufficient conditions for the formation of trapped surfaces in a class of nonspherical systems are proven. Massive singularities, if they exist in the geometries discussed, are always surrounded by apparent horizons. Milder singularities that are strongly nonspherical might be naked. Implications concerning the validity of the hoop conjecture are discussed.

We show a mechanism using a discrete symmetry, the dicyclic group ${\mathrm{Q}}_6$, which naturally gives rise to a small mass but a large transitional magnetic moment for the neutrino such that the anticorrelation between the solar neutrino intensity and the sunspot activity can be explained. The process of muonium-antimuonium oscillation provides the most interesting constraint to the model besides neutrino physics.

We report the most sensitive direct upper limit set on the mass ${\mathit{m}}_{\nu }$ of the electron antineutrino. Our measurements of the shape of the β decay spectrum of free molecular tritium yield, under the assumption of no new physics other than that of mass, a central value for ${\mathit{m}}_{\nu }^2$ of -147±68±41 ${\mathrm{eV}}^2$, which corresponds to an upper limit of 9.3 eV (95% confidence level) on ${\mathit{m}}_{\nu }$. The result is in clear disagreement with a reported value of 26(5) eV.

Nucleon self-energies in nuclear matter are studied by analyzing the correlator of nucleon interpolating fields using QCD sum-rule methods. Large Lorentz scalar and vector self-energies arise naturally, and are comparable to the optical potentials of Dirac phenomenology. The key phenomenological inputs are the baryon density and the value of the nucleon σ term.