We have measured the surface impedance ${\mathit{Z}}_{\mathit{s}}$=${\mathit{R}}_{\mathit{s}}$+${\mathit{iX}}_{\mathit{s}}$ in the normal and superconducting states of κ(BEDT-TTF${)}_2$Cu(NCS${)}_2$, and have evaluated the conductivity ${\mathrm{\sigma }}_1$. The temperature-independent ${\mathit{X}}_{\mathit{s}}$ for T≪${\mathit{T}}_{\mathit{c}}$ and the weak maximum observed for ${\mathrm{\sigma }}_1$ below ${\mathit{T}}_{\mathit{c}}$ rule out unusual pairing. Our results are in good overall agreement with calculations based on a BCS ground state.

Using the braid-group formalism we study the consequences of gauge invariance for fractionally charged anyonic quasiparticles in a two-dimensional multiply connected system. It is shown that gauge invariance requires multicomponent wave functions, and leads to the emergence of a hidden topological ${\mathit{Z}}_{\mathit{n}}$ symmetry with associated quantum number and unavoidable occurrence of level crossings for many-body eigenstates. In certain situations, it relates the fractional charge to anyon statistics. The implications for the fractional quantum Hall effect are also discussed.

We show that low-frequency structure in the infrared reflectance of the high-temperature superconductor ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ results from the electron-phonon interaction. Characteristic antiresonant line shapes are seen in the phonon region of the spectrum and the frequency-dependent scattering rate of the mid-infrared electronic continuum has peaks at 150 ${\mathrm{cm}}^{\mathrm{-}1}$ (19 meV) and at 360 ${\mathrm{cm}}^{\mathrm{-}1}$ (45 meV) in good agreement with phonon density-of-states peaks in neutron time-of-flight spectra that develop in superconducting samples. The interaction between the phonons and the charge carriers can be understood in terms of a charged-phonon model.

Electron-energy-loss experiments of ${\mathrm{H}}_2$ physisorbed on noble metals at low temperature indicate that the ortho-para conversion rate is 2 orders of magnitude faster on a Ag(111) surface than on a Cu(100) one. We suggest a process in which a metal electron is virtually transferred back and forth from a surface band to the molecle antibondoing orbital, ortho-para energy being dissipated by metal (electron-hole) triplet pairs. The ortho-para rates are about 1 min on Ag(111) and 1 h on Cu(100), in agreement with experimental data. This large difference does not characterize Ag and Cu, but is inherent to different surface orientations.

The transition from the dangerous cardiac arrhythmia, ventricular tachycardia, to the fatal cardiac arrhythmia, ventricular fibrillation, is believed to be associated with the breakup of spiral waves of excitation into multiple reentrant waves. A new computational method for wave propagation in discrete excitable media employing coupled maps with continuous time is used to derive analytical criteria for parameter ranges in which spiral waves show a stationary rotation, wandering, and breakup into multiple spirals.

I show that Weinberg’s nonlinear quantum mechanics leads either to communication via Einstein-Podolsky-Rosen correlations, or to communications between branches of the wave function.

We study the massless scalar wave equation on a class of asymptotically flat, static spacetimes with closed timelike curves (CTC’s), in which all future-directed CTC’s traverse one end of a handle (wormhole) and emerge from the other end at an earlier time. Existence of smooth, asymptotically regular solutions is proved for smooth data with finite energy given in ${\mathit{scrI}}^{\mathrm{-}}$. The proof requires a generalized spectral decomposition for a non-Hermitian operator. We also prove that this solution is unique among solutions that die off in time.

This Letter points out that partial coherence effects may result in distant objects apparently fluctuating in intensity and structure as a result of motion of the observer with respect to the source. It is suggested that these effects may play a role in explaining the intensity fluctuations and superluminal velocities observed in astrophysical objects such as quasars.

A serious breakdown of the distorted-wave impulse approximation has recently been observed in the proton-knockout reaction ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(e,e’p${)}^3$H. In the phenomenological description of the data, charge-excnange contributions were included through a coupled-channel calculation. New data obtained in a wide range of kinematical configurations are presented in order to study the anomaly in more detail. Its magnitude and dependence on momentum transfer are well accounted for by a newly presented microscopic description of various interaction effects, including meson-exchange currents and charge-exchange processes.

The first spectroscopic evidence of a double-bridged silicon molecule is reported. The submillimeter-wave rotational spectrum of the disilyne ${\mathrm{Si}}_2$${\mathrm{H}}_2$ has been observed in a low-power silane plasma cooled at liquid-nitrogen temperature, with argon as buffer gas. These measurements led to the determination of the ${\mathit{r}}_0$ structure, which is in good agreement with ab initio calculations. This nonclassical structure is confirmed by the observation of the ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ monosubstituted forms.

A new interference mechanism, analogous to ‘‘classic’’ double-slit electron scattering, has been identified in low-energy ion-atom collisions. This Coulomb ‘‘path’’ interference results from the existence of two trajectories, indistinguishable with respect to laboratory energy and emission angle, along which ejected autoionizing electrons may be scattered by the attractive Coulomb potential of the slowly receding spectator ion. A simple semiclassical description is presented. Calculated model line shapes are in excellent ageement with the strong angular dependence of the interference structure observed in the He-target 2${\mathit{s}}^2$ ${}_{}{}^1{}_{}{}^{}$S autoionizing line shape measured near 0° following 10-keV ${\mathrm{He}}^{+}$+He collisions.

Local particle and heat transport coefficients have been measured in a temperature scan of neutral-beam–heated plasmas with n, ${\mathit{I}}_{\mathit{p}}$, and ${\mathit{B}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$ held constant. The electron transport is ascertained from a flux analysis of a small density perturbation, and the heat transport is obtained from the equilibrium power balance. The transport coefficients vary as ${\mathit{T}}_{\mathit{e}}^{\mathrm{\alpha }}$, where α=1.5–2.5. The observed temperature dependence is predicted by numerical calculations of anomalous transport due to trapped-particle drift-type microinstabilities.

The instability of a magnetically confined plasma against macroscopic modes is analyzed in collisionless regimes where magnetic reconnection occurs because of finite electron inertia and the ion gyroradius ${\mathrm{\rho }}_{\mathit{i}}$ replaces the skin depth d as the width of the mode boundary layer. Growth rates γ/${\mathrm{\omega }}_{\mathit{A}}$∼(d/${\mathit{r}}_{\mathit{s}}$)(${\mathrm{\rho }}_{\mathit{i}}$/d${)}^{2/3}$ are found, with ${\mathrm{\omega }}_{\mathit{A}}$ the Alfvén frequency and ${\mathit{r}}_{\mathit{s}}$ the radius of the reconnecting surface. For typical JET parameters, ${\gamma }^{\mathrm{-}1}$∼50–100 μs, which compares favorably with the observed instability growth time of internal plasma relaxations.

In order to produce and study the ion-temperature-gradient instability, the Columbia Linear Machine has been modified to yield a peaked ion temperature and flattish density profiles. Under these conditions the parameter ${\mathrm{\eta }}_{\mathit{i}}$ (=d ln${\mathit{T}}_{\mathit{i}}$/d lnN) exceeded the critical value and a strong instability has been observed. Further identification has been based on observation of the azimuthal and axial wavelengths, and the real frequency, appropriate for the mode.

Using time-resolved electron-energy-loss spectroscopy coupled with a dual-molecular-beam technique, we have detected and characterized a two-dimensional methane gas-liquid phase transition on a clean Ag(110) surface. Quasiequilibrium measurements of both adsorption isobars and desorption isotherms are presented. These data are simultaneously analyzed using a simple statistical thermodynamic model in which the adsorbed-phase chemical potential is expressed by a virial expansion. The applicability of the quasiequilibrium assumption in treating coverage-dependent desorption data is strongly supported by our results.

A simple generalization of a continuum model of fluctuating membranes is considered in which one allows the existence of holes as structural defects. The proposed phase diagram of such systems includes, in particular, a variety of ‘‘sponge’’ phases now exhibiting edges in the form of closed loops or infinite lines. We show that the simplest theory describing the transitions between these phases is identical to the lattice gauge theory for a ${\mathit{Z}}_2$ Higgs system. We suggest, therefore, that sponge phases of amphiphilic films could form experimental models to check some of the nontrivial predictions of lattice gauge theories.

The dynamic roughening of a growing crystalline facet is reexamined by including nonlinear effects. A new and unusual fixed point controls the crossover between rough and faceted growth. Unlike linear treatments, the dynamics is no longer diffusive, and an anomalous decrease in mobility is predicted. Implications of these results for recent numerical simulations of growth and experiments on He films are discussed.

We show that the full boundary integral equation reduces, for small Péclet numbers, to a nonlinear similarity equation which contains only two dimensionless parameters, σ=${\mathit{d}}_0$l/${\lambda }^2$ and χ=l/${\mathit{l}}_{\mathit{T}}$, where ${\mathit{d}}_0$, l, and ${\mathit{l}}_{\mathit{T}}$ are the capillary, diffusion, and thermal lengths and λ is the wavelength of the pattern. All physical quantities should depend on σ and χ only. This is confirmed by numerically integrating the original equations. The selected wavelength should scale as λ∼${\mathit{V}}^{\mathrm{-}1/2}$f(l/${\mathit{l}}_{\mathit{T}}$) (V is the velocity). Our results suggest that λ∼${\mathit{V}}^{\mathrm{-}\mathrm{\alpha }}$, where α≃1/2 for large V and α<1/2 for small V. Our results agree with experiments and we propose further experimental tests.

We show that for some chiral compounds the field-induced molecular tilt in the smectic-A phase undergoes a peculiar sign inversion with respect to the layer normal as temperature increases. The electroclinic response of the system to an external electric field completely disappears at a characteristic temperature. This unusual behavior can be described in terms of a dynamically fluctuating mixture of at least two conformers that are separated by an energy barrier in their liquid-crystalline states. It is found that the energy barrier between these two conformers is comparable to the rotational barrier in normal hydrocarbons.

By identifying anisotropic scaling as the dominant feature of a lattice gas driven by a strong electric field, I obtain finite-size scaling forms by extending exact field-theoretic results. These are texted and supplemented by extensive Monte Carlo simulations in two dimensons. Excellent agreements are found. This resolves the disagreements between simulations and theories on the universality of the related models. Novel features of the finite-size effects of intrinsically anisotropic systems are emphasized.