We present the nonlinear phase equations describing the stability of a one-dimensional periodic pattern, with mean flow effect due to Galilean invariance. We show that the phase dynamics is second order in time, and could lead to an oscillatory instability of the pattern.

A novel mechanism capable of efficiently modulating intense relativistic electron beams is reported. This mechanism uses unique properties of slow and fast charge-density waves on an intense beam of a finite transverse dimension. The mechanism was investigated with use of an external microwave energy to excite these waves on a beam. Large-amplitude coherent and monochromatic current oscillations were detected on the electron beam at the same frequency as the external source. With use of this mechanism it becomes possible to construct efficient microwave amplifiers suitable for large rf accelerators.

We demonstrate that a liquid suspension of microparticles can be utilized to generate harmonic phase conjugate waves. This phenomenon involves the formation of higher-order particle gratings via electrostrictive forces generated by the low-frequency pump and probe fields. In turn, such gratings can coherently scatter high-frequency pump radiation, oscillating at a harmonic of the probe wave to form a conjugate wave oscillating at the same frequency.

Globally coherent modes which are observed during formation in the S-1 Spheromak plasma occur during flux conversion and plasma relaxation toward a minimum-energy state, suggesting that these modes provide a means for relaxation. A significant finding is the temporal progression of these modes through a sequence n=5,4,3,2, m=1, as q rises through rational fractions m/n, where n and m are defined by the functional dependence $e^{i(n\phi +\mathrm{mtheta})}$ of the fluctuations on toroidal angle φ and poloidal angle theta. Comparison with theory of the observed modes and the sequence of occurrence suggests that these modes are due to resistive MHD instabilities.

The Ni diffusivity and composition profile were measured in an amorphous Ni-Zr alloy formed in a Ni/a-NiZr/Zr binary diffusion couple. The Ni diffusion coefficient at 250 °C was found to be 1×${10}^{\mathrm{-}16}$ ${\mathrm{cm}}^2$/sec. The concentration profile within this amorphous phase is linear and the compositions at the interfaces between the amorphous alloy and the pure Ni and pure Zr tend to the constant values of 68% Ni and 47% Ni, respectively.

The structural origin of the resistivity anomaly occuring in the α phase of some rare-earth–hydrogen systems is elucidated in ${\mathrm{LuD}}_{\mathrm{x}}$ via a diffuse neutron-scattering experiment. The results give evidence of a peculiar linear ordering tendency where second-neighbor tetrahedral sites along the hexagonal c axis are occupied.

The equation-of-motion technique has been used to study the optic response functions of a computer-generated periodic random network containing 1536 ions. Long-range Coulomb effects were included for the first time. Our results show unambiguously the existence of an LO-TO splitting. The long-wavelength LO response function peaks at the band edge in the density of states and is very sharp, whereas the log-wavelength TO response function peaks at a lower frequency and is much broader.

We show that the α-(AlMnSi) crystal structure is closely (and systematically) related to that of the icosahedral Al-Mn-Si alloys. Using a modification of the ‘‘projection’’ method of generating icosahedral structures from six-dimensional lattices, we find a simple description of the α-(AlMnSi) structure. This structure, and (we conjecture) the icosahedral one, can also be described as a packing of 54-atom icosahedral clusters.

The phase change of the wave function of a superfluid film as a vortex moves around a closed path counts the number of superfluid particles enclosed by that path. This result is used to investigate whether such vortices obey ‘‘fractional statistics.’’ We conclude that this is not the case in compressible superfluids such as ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films.

An investigation of configurational properties of the thermodynamic ensemble of linear polymers during equilibrium polymerization is initiated. Our Monte Carlo calculation performed on a square lattice using the Jarić-Bennemann model indicates a nonuniversal temperature- and stiffness-dependent asymptotic power-law behavior of the average square radius of gyration for polymers of a given weight S, R¯ ${}_{}{}^2{}_{}{}^{}$(S,T)≊A(T)${\mathrm{S}}^{\nu \left(\mathrm{T}\right)}$. In the limit of zero temperature, the average polymer weight and the average square radius of gyration diverge as R¯ ${}_{}{}^2{}_{}{}^{}\mathrm{¯}$ ${}_{}{}^{\nu }{}_{}{}^{}$, where the exponent ν≊ν(0) depends on stiffness and differs from the Flory and Gaussian values.

Proton spin-lattice relaxation times ($T_1$) measured for the first time across a random transition-metal alloy system, ${\mathrm{V}}_{\mathrm{x}}$${\mathrm{Nb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{H}}_{0.2}$, from 100 to 700 K reveal (a) a suppression of hydride phase precipitation at low temperatures accompanied by enhanced retention of hydrogen in the solid-solution (α) phase compared to pure V or Nb, (b) hydrogen motion in the α phase at intermediate compositions governed by a distribution of activation energies, and (c) a transition to short, almost temperature-independent, $T_1$ behavior in α-${\mathrm{V}}_{0.1}$${\mathrm{Nb}}_{0.9}$${\mathrm{N}}_{0.2}$ consistent with localized hydrogen motion around attracting V atoms.

The evolution of ${\mathrm{TiH}}_2$ aggregates formed from an amorphous hydrogenated CuTi alloy has been measured by small-angle neutron scattering as a function of temperature. The total correlation function has been used to determine both fractal dimension D and crossover length ξ which are found to increase with temperature. The temperature range studied can be divided into three regions corresponding respectively to the formation, restructuration, and growth of the aggregates. This evolution is related to the variation of the hydrogen content and to its mobility inside the sample.

The structure of a monolayer of pentadecanoic acid near the liquid-expanded–liquid-condensed phase transition at a water-air interface is studied by optical second-harmonic generation. The results show that this transition is accompanied by a reorientation of the molecules and that the two phases are separated by an inhomogeneous coexistence region on the isotherms.

The growth of nematic films near a wall close to the nematic-isotropic transition is studied for planar boundary conditions. If the nematic phase wets the wall, near the onset of bulk nematic behavior the nematic film near the wall is in a Kosterlitz-Thouless low-temperature phase. The transition to this phase can be a defect-unbinding transition or a first-order transition, or two transitions may occur. A surface phase diagram is drawn as a function of temperature, bulk ordering field, and surface ordering field.

We describe experiments in which quasi one-dimensional wires are doped with magnetic impurities at submicron intervals. The discrete doped regions serve as ideal probes of the spatial extent of the interference effects responsible for the weak-localization corrections to conductance. The experiments are the first direct comparison of Thouless’s length-dependent conductance prediction to an accurate length scale.

The density of states for a tight-binding Hamiltonian on a two-dimensional Penrose lattice is computed numerically by the continued fraction recursion method. The result shows evidence of a strong Van Hove–type singularity which is remarkable for a system possessing no long-range periodic translational order. By a method of finite-size scaling extrapolation the exponent α and amplitude C, where ρ(E)∼${\mathrm{CE}}^{\mathrm{-}\mathrm{\alpha }}$, are estimated to be α=0.09±0.05 and C=exp(3.8±0.2).

In the non-Ohmic regime the total differential conductivity of ${\mathrm{NbSe}}_3$ obeys a simple scaling relationship when the Ohmic conductivity ${\mathrm{\sigma }}_0$ is used as the scaling parameter, viz., dj(E,${\mathrm{\sigma }}_0$)/dE=g(${\mathrm{\sigma }}_0$)+f(${\mathrm{\sigma }}_0$ )E. This equation is valid for fields E varying from 2${\mathrm{E}}_{\mathrm{T}}$ up to 500${\mathrm{E}}_{\mathrm{T}}$ at 50 K (where ${\mathrm{E}}_{\mathrm{T}}$ is the threshold field). We have also verified it over the range of temperatures 50 K>T>15 K. Implications for the theory of charge-density-wave transport are discussed.

A particle in a chaotic region of phase space can spend a long time near the boundary of a regular region since transport there is slow. This "stickiness" of regular regions is thought to be responsible for previous observations in numerical experiments of a long-time algebraic decay of the particle survivial probability, i.e., survival probability $\sim t^{-z}$ for large $t$. This paper presents a global model for transport in such systems and demonstrates the essential role of the infinite hierarchy of small islands interspersed in the chaotic region. Results for $z$ are discussed.

An operational procedure is given for determining experimentally, in principle at least, the Wigner function for an ensemble of particles. This manner of "measuring" a quantum state, whether pure or mixed, via its Wigner function, seems the simplest possible, and closely parallels the method one might use in classical mechanics to determine a (true) phase-space probability density.

We have studied inclusive $K_S$, $\Lambda$, and $\overline{\Lambda }$ photoproduction over the ranges $40<\mathrm{}{E}_{\gamma }<170\mathrm{}$ GeV and forward produced mass $2<\mathrm{}{M}_F<10\mathrm{}$ GeV. We observe equal $\Lambda$ and $\overline{\Lambda }$ production rates and spectra as expected in a diffractive process where the target proton remains unaltered. We show that the fraction of hadronic events with a strange particle produced in events with forward mass $M_F$ agrees well with the same measurement in $e^{+}{e}^{-}$ annihilation at a center-of-mass energy $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=M_F$. The $x=\frac{2P}{M_F}$ distributions of these three particles in the forward-mass rest frame are compared with theoretical predictions.