We study a forced symmetric oscillator containing a saturable inductor with magnetic hysteresis, approximated by a noninvertible map of the plane. The system displays a Hopf bifurcation to quasiperiodicity, entrainment horns, and chaos. Behavior near points of resonance (weak and strong) is found to correspond well with Arnold's theory. Within an entrainment horn, we observe symmetry breaking, period doubling, and complementary band merging. The symmetry behavior is explained by use of the concept of a half-cycle map.

The use of two lasers is suggested to freeze microbunches in an optical klystron harmonic generator, and a third laser beam to be sent onto the microbunches. It is shown that under certain conditions there can be intense generation of coherent soft x rays. The calculation of the power indicates the possibility of one-shot x-ray holography.

We report observation of bifurcations, higher harmonics, and chaos in an all-optical quantum system. These phenomena occur in a passive Fabry-Perot resonator, in association with deep and sustained Ikeda modulation of smooth input pulses. Results are in excellent agreement with our adaptation of optical bistability theory to the time-dependent regime.

A magnetic field $B$ is found to be convected by the electron heat flux ${\overrightarrow{\mathrm{q}}}_e$ because of the Nernst effect, i.e., with a velocity ${\overrightarrow{\mathrm{V}}}_T \left(\sim \frac{2{\overrightarrow{\mathrm{q}}}_e}{3n_e{T}_e}\right)$. In laser-driven ablation the convection is towards the overdense region and $B$ can be amplified by 10-100 times because $\nabla ·{\overrightarrow{\mathrm{V}}}_T<0\mathrm{}$, making $\frac{B}{n_i}$ and hence ${\omega }_e{\tau }_e$ almost constant for ${\lambda }_{\mathrm{mfp}}>\frac{c}{{\omega }_{\mathrm{pe}}}$. The spatially extended and amplified magnetic field can inhibit hot-electron transport, reducing preheat. For ${\omega }_e{\tau }_e>1\mathrm{}$, the critical and ablation surfaces are brought closer together, which increases hydrodynamic coupling.

An electron beam with a current exceeding 200 A has been generated and sustained by continuous injection of electrons into a rising toroidal and vertical magnetic field. There is a large mismatch between the electron energy and the vertical field. When the vertical field reaches a certain strength, accelerated beam electrons hit the outer wall of the torus, destroying the beam. By control of this vertical field the lifetime of the beam is extended yielding an electron energy of ∼ 1 MeV.

Model equations are proposed in an attempt to take into account the self-consistency effects which invalidate the quasilinear theory in one dimension. The diffusion coefficient and mode growth rate are found to be increased as compared with their quasilinear predictions.

By use of C${\mathrm{O}}_2$ laser scattering, parametrically excited lower hybrid waves were observed in the Alcator C tokamak. The power spectrum had a maximum at $N_{\parallel }\gtrsim 7$, in contrast to the pump-wave spectrum which peaked near $N_{\parallel }\simeq 3$ ($N_{\parallel }$ is the index of refraction parallel to the magnetic field). Ion tail formation near the plasma edge correlated well with the occurrence of parametric decay. The consequence of these phenomena on wave propagation into the plasma interior is discussed.

Using the cluster-variation method in the tetrahedron approximation, we study order-disorder transitions at the (100) surface of Cu-Au alloys. Depending on surface segregation, the order-disorder transition may be first or second order. Disordering of the surface may occur at temperatures above or below the bulk transition temperature. The recent low-energy ion-scattering data on ${\mathrm{Cu}}_3$Au is interpreted as evidence for stronger long-range order at the surface than in the bulk.

Combination of high-resolution surface infrared spectroscopy on single-domain Si(100)-(2×1)H and ab initio cluster calculations provides a complete determination of the geometry and vibrational parameters for the monohydride structure.

Zinc metal leaves are grown two-dimensionally by electrodeposition. The structures clearly remind us of the random patterns simulated by computer according to the Witten-Sander diffusion-limited-aggregation model. The scale invariance is tested by computing the density-density correlation function for the digitized patterns of the photographs. The Hausdorff dimension averaged over many examples is $D=1.66\mathrm{}\pm 0.03$, which is in excellent agreement with that of the two-dimensional diffusion-limited-aggregation model ($D\cong \frac{5}{3}$).

The decay of ${}_{}{}^{111}{}_{}{}^{}\mathrm{Sn}$ to ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ via electron capture is employed for the first observation of a solid-state effect caused by nuclear recoil due to neutrino emission. The monoenergetic ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ recoil atoms of 29 eV start from substitutional lattice sites in copper and produce isolated, single Frenkel pairs. The effect is traced by observation of $\gamma \gamma$ perturbed angular correlations following the decay ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ to ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$.

The behavior of the Si(111)-(7 × 7) and the Si(100)-(2 × 1) surfaces upon room-temperature deposition of Ge is investigated with Auger-electron spectroscopy, low-energy electron diffraction, and Rutherford backscattering channeling techniques. The Ge over-layers form a sharp, but highly disordered, interface with no indication of island formation. It is found that the Ge relieves the reconstruction of the Si(100)-(2 × 1) surface but not of the Si(111)-(7 × 7) surface.

High-pressure studies have shown that $\mathrm{K}{\mathrm{Ta}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ crystals with small $x(\approx 0.02)$ exhibit relaxational glasslike behavior rather than a static ferroelectric structural phase transition as previously thought. The results show a pressure-induced transition from frozen to relaxing impurity behavior and evidence for an off-center to on-center transition of the Nb ion at the $B$ site of the perovskite lattice.

An exact path-integral solution of the Dirac equation with a Coulomb potential is found. The energy-dependent Green's function of the second-order Dirac-Coulomb equation, expressed as a polar-coordinate path integral, is reduced to the exactly solvable path integral for an isotropic harmonic oscillator by a coordinate transformation combined with a local time rescaling. The Green's function of the linear Dirac equation is evaluated with the help of the Biedenharn transformation. The energy spectrum for the bound states is also obtained.

We obtain the rule governing many-body wave functions for particles obeying fractional statistics in two (space) dimensions. It generalizes and continuously interpolates the usual symmetrization and antisymmetrization. Quantum mechanics of more than two particles is discussed and some new features are found.

We show that the collision time may be interpreted as the time average of a flux-flux correlation function. This interpretation leads quantum mechanically to a complex time whose real part is identical to the usual definition as provided by F. T. Smith. The imaginary part is identical, in the semiclassical limit, to the imaginary time associated with tunneling.

We derive for the first time second-order gradient corrections to the Thomas-Fermi kinetic-energy and entropy density functionals for a fermion system at finite temperature. Density variational calculations for a heated nucleus with a Skyrme interaction lead to excellent agreement with results of Hartree-Fock calculations.

Self-avoiding random surfaces are analyzed by renormalization-group methods. The Hausdorff dimension $\frac{1}{\nu }$ and the critical plaquette fugacity are computed for different dimensionalities $d$; in particular, $\nu =\frac{1}{2}-\frac{\epsilon }{4}+O\left({\epsilon }^2\right)$ for $d=2+\epsilon$. The model describes "sheet polymers" in a good solvent: A Flory type of argument yields $\nu =\frac{3}{\mathrm{}(4+d)\mathrm{}}$, in good agreement with the renormalization results, and a critical dimensionality $d_c=8\mathrm{}$, with $\nu =\frac{1}{4}$.

For individual helicity amplitudes, asymptotic QCD gives results which differ from standard nuclear physics. For the deuteron electromagnetic form factors, QCD predicts $G_C=\left(\frac{Q^2}{6M_d^2}\right)G_Q$ at high $Q^2$. This gives a result for the polarization ratio $\frac{p_x}{p_{\mathrm{xz}}}$ which is dramatically different from predictions of several standard deuteron wave functions. Polarization-transfer measurements of the deuteron form factor in this $Q^2$ region are therefore a sensitive test of the validity of perturbative QCD for exclusive processes at these momentum transfers.

Proton production in $e^{+}{e}^{-}$ annihilation at 29 GeV has been studied with the time projection chamber. Measurements of the dependence of proton fractions on momentum, transverse momentum with respect to the jet axis, hadron multiplicity, and event sphericity are reported. Our results are consistent with the assumption that primary baryons and mesons have similar production spectra, and indicate that protons provide more direct probes of underlying fragmentation phenomena than do pions.