Analysis of interacting fermion systems shows that there are two fundamentally different fixed points, Fermi-liquid theory and ‘‘Luttinger-liquid theory’’ (Haldane), a state in which charge and spin acquire distinct spectra and correlations have unusual exponents. The Luttinger liquids include most interacting one-dimensional systems, and some higher- (especially two) dimensional systems in which the band spectrum is bounded above, systems with Mott-Hubbard gaps and an upper Hubbard band. We give a theory which is useful in calculating normal-state, and some superconducting, properties of high-${\mathit{T}}_{\mathit{c}}$ superconductors.

A hierarchical approach to complexity of infinite stationary strings of symbols is introduced by investigating the scaling behavior of suitable quantities. The topological entropy, which estimates the growth rate of the number of admissible words, corresponds to the first-order indicator ${\mathit{C}}^{\mathrm{}\left(1\right)\mathrm{}}$. At the second level, a novel indicator ${\mathit{C}}^{\mathrm{}\left(2\right)\mathrm{}}$ is introduced which measures the growth rate of the number of irreducible forbidden words. Finally, a detailed analysis of 2D maps reveals that ${\mathit{C}}^{\mathrm{}\left(2\right)\mathrm{}}$ can be expressed in terms of the Lyapunov exponents.

We study a general Bak-Tang-Wiesenfeld–type automaton model of self-organized criticality in which the toppling conditions depend on local height, but not on its gradient. We characterize the critical state, and determine its entropy for an arbitrary finite lattice in any dimension. The two-point correlation function is shown to satisfy a linear equation. The spectrum of relaxation times describing the approach to the critical state is also determined exactly.

It is pointed out that scaling (multifractal) properties of chaotic repellers underlying irregular scattering in two-degrees-of-freedom systems can be deduced by measuring simple length scales generated hierarchically along a straight line taken far away from the interaction region, or on the Poincaré plane, and analyzing them in the spirit of the thermodynamic formalism. The method is easier to apply than a periodic orbit analysis.

We incorporate linear mode conversion in wave-kinetic theory when the incoming waves are incoherent, as occurs when the wave sources are turbulent processes or thermal emission. Mode conversion takes place when the rays of either wave mode cross the mode conversion manifold in the ray phase space. Jump conditions are derived which match the incoming and outgoing wave actions across the mode-conversion manifold, leading to a pair of coupled wave-kinetic equations. We also discuss how incoherent linear mode conversion acts as a source of wave entropy.

An exact asymptotically flat solution of the vacuum Einstein equations representing the exterior gravitational field of a stationary axisymmetric mass with an arbitrary mass-multipole structure is presented.

The emission of neutral particles from Cygnus X-3 has been searched for at energies above 5×${10}^{17}$ eV, using data from the Akeno 20-${\mathrm{km}}^2$ air-shower array spanning the period December 1984 to July 1989. A 3.5σ dc excess is observed aroung the Cygnus X-3 region. This excess corresponds to a flux of (1.8±0.7)×${10}^{\mathrm{-}17}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\mathrm{s}}^{\mathrm{-}1}$ above 5×${10}^{17}$ eV, in agreement with the Fly’s Eye data, but not the Haverah Park data. The signals do not show any 4.8-h periodicity. Their arrival times seem to be bunched in correlation with event-rate increases observed at ${10}^{16}$ eV with the Akeno 1-${\mathrm{km}}^2$ array.

We examine bosonic zero modes of vortices formed in the gauge breaking G→H. For non-Abelian G, zero modes are generic. Their solutions depend on global symmetry structure. Vortices render the embedding H⊂G space dependent, with a dynamically determined subgroup H̃ single valued. They Aharonov-Bohm scatter gauge bosons associated with multivalued generators. Alice strings (H=O(2), H̃=${\mathit{openZ}}_2$) attract charges and scatter SO(2) ‘‘photons,’’ and a two-string system has zero modes with unlocalizable ‘‘Cheshire’’ charge. The resulting superconductivity has novel electrodynamics.

The ‘‘spin’’-two and scalar physical propagating fields of the third massive level of the open bosonic string are shown to be mere gauge artifacts of the higher-‘‘spin’’ fields at the same mass level. This is demonstrated by requiring the worldsheet conformal symmetry in the weak-background-field approximation and is argued to be a σ-model four-loop result. It is conjectured that this phenomenon comes from the well-known ambiguity in defining the positive-norm states due to the existence of zero-norm states in the same Young representation.

We consider the addition of the Chern-Simons action to non-Abelian gauge theories at one-loop order.. It is found that the topological mass acquired by the gauge field tends to assist the breaking of the gauge symmetry in the presence of destructively interfering adjoint-class matter fields. When the matter fields are massless, a critical length may be found above which symmetry is broken. When massive matter is also included there is no critical length, but a critical ratio between the Chern-Simons mass and the matter-field mass.

In this paper we found, by explicitly solving the Dirac equation, the complete energy spectrum and the corresponding eigenfunctions, for both the positive- and the negative-energy states, of the recently proposed Dirac oscillator. We found the electromagnetic potential associated with its interaction term. This exactly soluble problem has a hidden supersymmetry responsible for the special properties of its energy spectrum. We discuss the implications of this supersymmetry in the stability of the Dirac sea and we calculate the related superpotential.

We have measured missing-energy spectra for the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(e,e’p) in the quasielastic region in parallel kinematics at momentum transfers q of 585, 775, and 827 MeV/c. We observed ${}_{}{}^1{}_{}{}^{}$p and ${}_{}{}^1{}_{}{}^{}$s single-proton knockout peaks and large broad strength attributed to multinucleon knockout. We saw no increase in strength at pion threshold. The ratio of single-particle knockout to a distorted-wave impulse-approximation calculation is approximately constant with q. Multinucleon knockout is 25%–40% of the total cross section; it increases with q. This quasielastic non-single-nucleon knockout is much stronger than previously observed.

Excited superdeformed bands have been observed in the N=86 isotones ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tb}$. The properties of these bands were found to closely resemble those of the yrast superdeformed bands in their Z+1 N=86 isotones ${(}^{151}$Tb and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Dy}$) such that, on average, the transition energies are identical to an accuracy of 1:1000. It is proposed that these excited superdeformed bands are based on single-proton excitations from the [301]1/2 orbital into the [651]3/2 intruder orbital and thus they are the first obsrevation of proton excitations in superdeformed nuclei.

The structure of recently discovered identical superdeformed bands in ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tb}$ and ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$, and in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tb}$ are discussed in terms of the strong-coupling approach. Based on the experimental evidence that the superdeformed core of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ is extremely insensitive to the polarization effects induced by the odd particle, the bands are shown to exhibit the presence of the pseudo SU(3) symmetry at extreme conditions of large elongations and high spins.

A new scheme has been developed that produces a slow atomic beam of high brightness with a narrow velocity distribution. The technique can provide long measurement times and high counting rates for future precision experiments. In our initial work, densities of ${10}^8$ Na atoms/${\mathrm{cm}}^3$ at a velocity of 270 cm/sec and at a temperature of ∼200 μK were obtained.

We report the first operation of a master oscillator-power amplifier in which both devices are free-electron lasers. Gain optimization in the power amplifier was studied. A 35-A electron beam produced up to 60% gain at 3 μm. The gain spectrum was obtained by gap tuning the power amplifier wiggler and evidence was found for violation of the Madey theorem due to high gain effects.

We report a unique dual nature of the magnetic-field-dependent resistive losses in epitaxial films of superconducting ${\mathrm{Y}}_2$${\mathrm{Ba}}_4$${\mathrm{Cu}}_8$${\mathrm{O}}_{16}$. For excitation currents coplanar with the magnetic field, the losses are identical in the Ohmic regime for both longitudinal and transverse field orientations. In the nonlinear current-voltage regime, the transverse field results in the Lorentz-force-induced instability in the fluxline lattice and a higher dissipation. Comparison of the flux-pinning potential in ${\mathrm{Y}}_2$${\mathrm{Ba}}_4$${\mathrm{Cu}}_8$${\mathrm{O}}_{16}$ deduced from the thermally activated nonlinear voltage with data on Y${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ suggests an important role of the increased separation between Cu-O superconducting planes in ${\mathrm{Y}}_2$${\mathrm{Ba}}_4$${\mathrm{Cu}}_8$${\mathrm{O}}_{16}$ in flux pinning.

In practice, large specimens of ferromagnetic materials settle into one of a large number of metastable states, not necessarily into the energetically lowest state. We suggest that they tend to select marginally stable states, in a manner similar to the process recently proposed by Bak, Tang, and Wiesenfeld. We apply this idea to the formation of the so-called zig-zag walls that separate oppositely magnetized domains in a magnetic recording tape.

A model combining thermally activated motion of flux lines, viscous flux flow at high current density, and distribution of activation energies is shown to reproduce the characteristic features of current-voltage curves of high-${\mathit{T}}_{\mathit{c}}$ superconductors. In particular the recent data of Koch et al. and Zeldov et al. can be explained without invoking a continuous phase transition (freezing into a superconducting vortex-glass phase) or a logarithmic current dependence of the activation energy.

The potential and angular dependence of second-harmonic generation from a metal-electrolyte interface has been measured. The perpendicular surface contribution to the harmonic polarization is found to be significant and to vary in a characteristic manner with the surface charge induced by the electrolyte. Both the overall magnitude of the surface polarization and its variation with applied potential are reproduced qualitatively by microscopic calculations based on the time-dependent density-functional approach.