Polymerized membranes or solidlike elastic sheets are studied by scaling arguments and Monte Carlo simulations. We find that the roughness exponent ζ has the value ζ=1/2 while previous simulations gave ζ=0.64±0.04. Our data are consistent with a finite value of the shear modulus on large scales. We also find a pronounced crossover from fluidlike behavior with ζ=1 on small scales to solidlike behavior with ζ=1/2 on large scales. This crossover should be observable in experiments on the flickering of red blood cells.

Two models coupling self-avoiding walks (SAWs) to Ising vacancies are studied. When the walk is performed on the hexagonal lattice and the vacancies are on the dual, an exact description of the behavior of the walk as a function of the Ising coupling is given. The walk collapses from SAW to FTHETA’-point behavior at the Ising critical point where its fractal dimension equals 11/8, as for the hull of Ising clusters. A walk on the square lattice, with vacancies either on the same or on the dual lattice, has SAW behavior even at Ising criticality. This is shown numerically and, within the conformal-invariance approach, poses a problem for which a conjectural solution is proposed.

Thermal fluctuations at equilibrium and excess fluctuations in the presence of transport in open multiprobe conductors are related to the scattering matrix of the conductor. The fluctuation-dissipation theorem for multiprobe conductors is discussed. A general expression for the excess noise in the presence of transport is derived. These results are applied to conductors which exhibit the quantized Hall effect. If backscattering is suppressed, excess noise is also suppressed.

We report resistive measurements on a thin-film analog of a modulated-transition-temperature superlattice. The aluminum film was reactive-ion etched in strips perpendicular to the current path, decreasing ${\mathit{T}}_{\mathit{c}}$ of the etched sections by ≊2%, thus spatially modulating the transition temperature. At current densities ≤600 A/${\mathrm{cm}}^2$, the resulting structures exhibit a single homogeneous transition for etched lengths up to 50 μm, substantially longer than expected from the order-parameter decay length of 0.81 μm for the proximity effect in the dirty limit.

It is shown that the long-wavelength limit of a doped spin-fermion model does not contain the Hopf invariant, when expanded around a staggered spin configuration. Furthermore, the resulting effective action that describes the destruction of long-range antiferromagnetic order by doping is an O(3) nonlinear σ model with coupling constants that depend on the dopant concentration.

High-quality antiferromagnetic (AF) superlattices (${\mathrm{FeF}}_2$${)}_{\mathit{m}}$(${\mathrm{CoF}}_2$${)}_{\mathit{n}}$, as judged from high-resolution x-ray diffraction (HRXD), were grown on (001) ${\mathrm{ZnF}}_2$ substrates. Using HRXD, the thermal-expansion coefficient ${\mathrm{\alpha }}_{\left[001\right]}$(T) vs T was measured. While two shifted AF anomalies are seen for (m,n)=(25,30), only one is observed for (m,n)=(19,6). Comparison of ${\mathrm{\alpha }}_{\left[001\right]}$(T) in the two superlattices with that of ${\mathrm{FeF}}_2$ and ${\mathrm{CoF}}_2$ indicates that a significant redistribution of the magnetic entropy occurs.

We report the first experimental study of the energy gap for the fractional quantum Hall states at Landau-level filling factors ν=1/3 and 2/3 in a variable-width electron system realized in a selectively doped, parabolic, AlGaAs quantum well. We observe a dramatic decrease in the measured energy gaps as the electron-layer thickness increases and the electric-subband separation decreases, which we interpret as the collapse of the correlated fractional states.

We have searched for photon signals in Υ(4S) decays, indicative of large decay rates involving annihilation of the bb¯ pair rather than decays to BB¯ meson pairs. We do not observe any evidence for such signals. We also obtain a model-independent upper limit of (4.5–6.0)% for the branching ratio of Υ(4S)→ggX, for 0<M(X)<1.2 GeV, at 90% confidence level.

Shell-model calculations have been carried out for isospin-forbidden β-delayed proton emission for 1s-0d-shell nuclei. The process in which a nucleus near the proton drip line ${\mathrm{\beta }}^{+}$ decays by a superallowed transition to the isobaric analog state in the daughter nucleus is considered. The first complete set of calculations for the subsequent isospin-forbidden particle decay of the isobaric analog state is presented. The decay channels considered include the processes of single-proton, sequential two-proton, direct two-proton, and α decay. The calculations reproduce the known data and suggest further experiments.

High-resolution photoelectron spectra (total instrumental width ≤0.1 eV) of the Si 2p core levels of ${\mathrm{SiH}}_4$ and ${\mathrm{SiF}}_4$ were obtained using the Aladdin undulator source. The vibrationally resolved Si 2p photoelectron spectrum of ${\mathrm{SiH}}_4$ yields a Si-H stretching energy of 0.295±0.002 eV for the core-hole ion and a lifetime width of ∼45 meV. Numerous vibrational lines are observed in the ${\mathrm{SiF}}_4$ Si 2p photoelectron spectrum. The Z+1 core-equivalent model is assessed and changes in the molecular geometries and bonding properties of the molecules upon ionization are discussed.

The n=2→n=1 lines of hydrogenlike and heliumlike uranium have been observed and are being reported for the first time. The spectrum consists of all allowed and forbidden lines. We have done a preliminary energy measurement of these lines with a precision in the (4–12)×${10}^{\mathrm{-}4}$ range.

We report improved measurements of the 10G-H, 10H-I, 10I-K, and 10K-L fine-structure intervals in atomic helium, obtained using fast-beam microwave-optical techniques. The measurement uncertainty is less than 1 kHz in each of sixteen measured intervals. The existence of very precise calculations of the nonrelativistic contributions to these intervals allows the measurements to be used to test relativistic and QED effects directly, and to confirm the predicted contributions from ‘‘retardation’’ forces due to two-photon exchange to better than 10%.

High-precision variational eigenvalues are presented for a range of helium Rydberg states up to n=10 and L=7. Convergence to a few parts in ${10}^{18}$ is obtained for many of the nonrelativistic eigenvalues. The results allow a clear assessment of the accuracy of asymptotic expansion methods extensively developed for states of high angular momentum. After adding relativistic and radiative corrections, a comparison with new high-precision measurements for transitions among the n=10 states is made. Contributions from the long-range Casimir-Polder effect are discussed.

Resonant transfer and excitation (RTE), resulting from simultaneous electron capture and K-shell excitation in a single collision, has been measured for 97–150 MeV/u ${\mathrm{U}}^{90+}$ ions in hydrogen. Distinct maxima, attributed to RTE contributions from the formation of intermediate excited states, were observed superimposed on a monotonically decreasing background due to single-electron capture. This measurement, the first for a very heavy projectile, provides a test of relativistic dielectronic-recombination theory.

Two autoionizing levels which are separated by a few decay widths may exhibit a sharp interference or window in their absorption profile and also make canceling contributions to the refractive index at the absorption minimum. A correct choice of intermediate mixing levels prevents a similar cancellation in the nonlinear susceptibility. Using uv lasers with energies of about a mJ and pulse lengths of 5 ns, we generate 0.23 μJ per pulse at 104.8 nm.

We have studied turbulent drag reduction using the technique of photon-correlation homodyne spectroscopy to measure turbulent velocity gradients in a dilute polymer solution. A large anisotropic suppression of turbulent velocity differences is found in the bulk region of the turbulent fluid and along the direction of the mean flow. The suppression effect is associated with an enhancement of the turbulent drag reduction. This anisotropy caused by polymer molecules in turbulent flow may be important in understanding turbulent drag reduction.

Results from a novel theory of radiatively enhanced tokamak edge turbulent transport are presented. A serious restriction on the impurity radiation drive is identified. In particular, due to a lack of pressure balance near a rational surface, the condensation effect does not survive. Consequently, the thermal instability drive is the only impurity radiation instability which remains. Our analysis consists of a theoretical calculation for the thermally driven drift-rippling mode model (φ̃,ñ,T̃,v${\mathrm{̃}}_{\mathrm{\parallel }}$). We present calculations of the edge fluctuations and the resultant transport coefficients versus radius.

The heat capaicty of submonolayer solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ films adsorbed on graphite has been measured for temperatures between 2 and 200 mK. Over a very narrow range of coverages an anomalously large nuclear-spin exchange is observed. This peak is analogous to the more dramatic anomaly previously observed for the second-layer system when compressed by a few overlying fluid layers. The implication is that the proposed indirect exchange involving the fluid atoms cannot be the responsible mechanism.

We calculate the deep-inelastic response of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. Using a universality hypothesis for the bridge function, we obtain a new, highly consistent ground-state Jastrow wave function with condensate fraction ${\mathit{n}}_0$≃0.081. The dynamics of final-state interactions is accounted for by a Monte Carlo sampling of the scattering wave function of the recoiling He atom. The results, in excellent agreement with recent neutron-scattering measurements, indicate that the response has a more complicated dependence on the structure of the ground state than is assumed by all previous theories.

This paper describes the first example of a consolute critical point associated with phase separation in a binary system of smectic liquid crystals. In particular, a homogeneous smectic-A mixture of a polar compound with an aliphatic tail and a nonpolar compound with a perfluoroalkyl tail separates on cooling into two coexisting smectic-A phases with different compositions. The characteristics of this system make it unique for the future investigation of the kinetics of spinodal decomposition in an anisotropic medium.