In the high-magnetic-field low-disorder limit the ground state at ν=1/5 Landau-level filling is an incompressible quantum liquid. This is determined by observing vanishing resistivity ${\mathrm{\rho }}_{\mathit{x}\mathit{x}}$ as the temperature T→0. At filling factors below ν=1/5 as well as in a narrow region above ν=1/5, ${\mathrm{\rho }}_{\mathit{x}\mathit{x}}$ diverges exponentially as T→0. This contrasts the T dependence at any higher ν. We conclude that the quantum liquid at ν=1/5 is surrounded by a different phase. In as much as the exponential divergencies are indicative of an electron solid this phase is reentrant in a narrow region above ν=1/5.

We report a definitive optical detection, using band-gap photoluminescence, of the integer and fractional quantum Hall effects in GaAs by a comprehensive study of integer states from ν=1 to 10 and the ν=2/3 hierarchy out to the 5/9 daughter state, in an ultrahigh-mobility single heterojunction at 120 mK.

Plateaus in the electron-hole recombination energy and minima in the peak intensity at integer and fractional filling factors occur in the luminescence from ultrahigh-mobility GaAs single quantum wells. At Landau and spin gaps the regions of plateaus and intensity minima broaden as the temperature is reduced, in consort with the transport Hall resistance. A sharp intensity minimum and peak shift is seen at ν=2/3, while higher-field fractions are characterized by a splitting in the luminescence. The optical anomalies are directly related to the position of the Fermi energy in localized transport states.

We describe the behavior of charges in two-dimensional arrays of normal-metal tunnel junctions with very small capacitance. A Kosterlitz-Thouless-Berezinskii phase transition with unbinding of charge-anticharge pairs occurs at a transition temperature of about ${\mathit{T}}_{\mathit{c}}$=${\mathit{e}}^2$/8π${\mathit{Ck}}_{\mathit{B}}$, with C the junction capacitance. We calculate the influence of tunneling conductance; ${\mathit{T}}_{\mathit{c}}$ is reduced with increasing conductance and no transition occurs for junction conductance above (14 kΩ${)}^{\mathrm{-}1}$. In the superconducting state a similar transition occurs at a 4 times higher ${\mathit{T}}_{\mathit{c}}$. We present the first experimental results on the conductive transition of an array in the normal and superconducting states.

The ground and the excited states of a two-dimensional anyon system are studied via finite-size numerical calculations in a spherical geometry. It is shown that Laughlin’s mean-field theory gives an accurate description of the ground-state properties of the finite, spherical system. We find, consistent with earlier analytic theories, that the collective mode of the system exhibits a linear dispersion in the long-wavelength limit, and predict a novel roton minimum at a finite value of the wave number q. We also discuss the consequences on the anyon spectrum of having a model repulsive interaction between the particles.

We show that the gauge character of interactions, which naturally appears in strongly correlated electron systems in the absence of long-range magnetic order, results in a linear T dependence of the resistivity.

Solubilization and conformational transitions of a polymer in dilute surfactant solutions are studied by dynamic light scattering. The polymer, poly(N-isopropylacrylamide), aggregates in aqueous solution when heated above 34 °C. A small amount of surfactant, sodium dodecyl sulfate, prevents aggregation—intermolecular solubilization takes place. The polymer then forms a stable dispersion of isolated collapsed globules. A further increase of the surfactant concentration leads to an expansion from the globule to the coil state due to intramolecular solubilization.

We propose here a new method to characterize the loss of memory with time in a chaotic system from a time series. This is done by introducing time-dependent generalized exponents. The asymptotic behavior can distinguish between chaotic systems which lose memory of the initial conditions completely, those which partially retain the memory, and those (borderline of chaos) which fully retain the memory. We give illustrative examples of the logistic and Hénon maps.

We consider a ball under the influence of gravity on a vibrating platform where the ball-platform collisions are completely inelastic. We present for the first time several remarkable features in the temporal behavior of the system; its phase space is divided into transmitting and absorbing regions, which are responsible for the abrupt termination of a period-doubling sequence and the onset of a locking regime, in which an appropriately defined winding number has intriguing scaling properties.

Decay rates of massive open strings are investigated at finite temperature. Employing the approximation method of Mitchell, Sundborg, and Turok, another meaning of the Hagedorn temperature for the open string theory is clarified: It is the limiting temperature where the picture of splitting probability per unit length is violated. Below the Hagedorn temperature the decay rates have the same values as in the zero-temperature system. Explicit numerical evaluations support our analysis.

Previous calculations of O(${\mathrm{\alpha }}_{\mathit{s}}^3$) corrections to inclusive jet production in hadron collisions are extended to finite-size jet cones and successfully compared with UA2 and CDF experimental data.

We derive a chiral weak Lagrangian which interpolates the QCD-corrected-four-fermion weak-interaction Lagrangian to low energies. This is done using the Nambu–Jona-Lasinio model as a guide. The derivation treats SU(3) breaking from the current-quark mass on an equal footing with the spontaneous chiral-symmetry breaking. It leads naturally to an additional factor of 2–4 enhancement of ΔI=1/2 K→ππ decay amplitudes.

The U(1) axial-vector form factor is studied using an unsubtracted dispersion relation. The associated axial charge is shown to be analytic in quark masses in the chiral limit although individual terms in the Cheng-Li separation exhibit large isospin and flavor-SU(3) symmetry breaking. A new separation of the U(1) axial charge is proposed, based on the wave functions of the physical states entering in the spectral density.

S+Au interactions at 200A GeV were observed using emulsion chambers, permitting measurement of pseudorapidities in the central region with precision ∼0.01 unit. Scaled-factorial-moment analyses are extended to bin sizes smaller than those accessible to other fixed-target experimental techniques. For a sample of 151 central collisions, moments are calculated using both ‘‘horizontal’’ and ‘‘vertical’’ analysis techniques. While the moments are found to rise (in a log-log plot) with decreasing pseudorapidity bin size δη, their slopes roll off to approximately zero for δη<0.1.

A sensitive study of the decay of the deformation-aligned K=14, 4-μs isomer in ${}_{}{}^{174}{}_{}{}^{}\mathrm{Hf}$ has revealed a multitude of the K-forbidden branches to the ground-state rotational band and other low-K bands, in competition with the known decays to high-K bands. The isomeric transitions have consistently low hindrance factors. These anomalous findings in an axially symmetric deformed nucleus severely test our understanding of the K-selection rule. The isomeric decay to an I=12 rotation-aligned state, and its mixing with the I=12 yrast state, provide a partial explanation.

The Ni-like 4d-4p laser scheme has been extended to wavelengths near the K absorption edge of carbon. A gain of 2.3 ${\mathrm{cm}}^{\mathrm{-}1}$ with a duration of 250 psec was observed in Ni-like Ta at 44.83 Å (a wavelength close to optimal for holographic imaging of live cells). Ni-like W produced a gain of 2.6 ${\mathrm{cm}}^{\mathrm{-}1}$ with a total of seven gainlengths of amplification at 43.18 Å. This is the first demonstration of an x-ray amplifier on the short-wavelength side of the carbon K edge, within the ‘‘water window.’’ Both lasers should be scalable to coherent power sufficient for holographic imaging and other applications.

Circular-limiter H modes are obtained on the TFTR tokamak during high-power neutral-beam heating. The transition is usually from the supershot to the H mode rather than the usual L to H transition, and thus is obtained in a low-recycling environment with core fueling mainly from the heating beams. As a result, the density and pressure profiles are highly peaked at the center. The global confinement time ${\mathrm{\tau }}_{\mathit{E}}$ is enhanced over L-mode scaling by up to ≊2.5 times. The onset of edge-localized MHD modes shortly after the H-mode transition appears to limit ${\mathrm{\tau }}_{\mathit{E}}$. Limiter H modes of up to 1.5 s duration have been realized.

The ion acoustic decay instability has been studied by monitoring the Stokes sideband of the second-harmonic emission from a laser-produced plasma. The intensity threshold decreased as the laser spot size increased. It reached homogeneous-plasma collisional values in planar plasmas produced using large laser spot sizes (D≳600 μm), for laser wavelengths of either 1.06 or 0.53 μm. These observations show that the ion acoustic decay instability may well play a more important role in laser fusion that had been generally believed.

A fully three-dimensional Rayleigh-Taylor instability of the pusher-fuel contact surface in a spherically stagnating system is investigated with the use of a new three-dimensional fluid code impact - 3d. Linear growth rates in the simulations agree quite well with analytical values which include spherical-geometry effects. Saturation amplitudes of the exponential growth and free-fall speed following the saturation are found to be, respectively, larger and faster than those of 2D simulations. Nonlinear bubble-spike structures are also studied in detail.

It is generally thought that the cholesteric liquid-crystal blue phases (BP), which are found near the transition to the isotropic liquid phase, are particularly favored by high chiralities. It is shown here, to the contrary, that the lattice structures of BP I and BP II are unstable in the limit of short pitch, and this instability leads, in turn, to a mechanism, which agrees with the available experimental evidence, for the formation of BP III, the seemingly amorphous blue phase.