Diblock copolymers in a selective solvent often assemble into spherical micelles. These micelles demonstrate long range order at moderate polymer concentrations. We explore the nature of the disorder-order transition in micellar suspensions through small angle x-ray diffraction studies. The phase behavior includes body-centered cubic (bcc) and face-centered cubic (fcc) lattices. We present the first phase diagram for block copolymer micelles to include both bcc and fcc structures and characterize the lattice selection by a ratio of coronal layer thickness to core radius.

We establish a correspondence between the evolution of the distribution of eigenvalues of a N×N matrix subject to a random Gaussian perturbing matrix, and a Fokker-Planck equation postulated by Dyson. Within this model, we prove the equivalence conjectured by Altshuler and co-workers between the space-time correlations of the Sutherland-Calogero-Moser system in the thermodynamic limit and a set of two-variable correlations for disordered quantum systems calculated by them. Multiple variable correlation functions are, however, shown to be inequivalent for the two cases.

We report the measurements of the de Haas–van Alphen (dHvA) effect for field ranges below and above the metamagnetic transition field (${\mathit{H}}_{\mathit{m}}$) in ${\mathrm{CeRu}}_2$${\mathrm{Si}}_2$. The dHvA frequency branches and the effective masses ranging from 1.5${\mathit{m}}_0$ to 120${\mathit{m}}_0$ observed below ${\mathit{H}}_{\mathit{m}}$ agree with the predictions of the itinerant f electron model, whereas those above ${\mathit{H}}_{\mathit{m}}$ can be explained well with the localized f electron model. All the dHvA frequencies change abruptly around ${\mathit{H}}_{\mathit{m}}$. The effective masses decrease considerably around ${\mathit{H}}_{\mathit{m}}$ and then continue to decrease with increasing field.

We present a theory of the magnetoplasmons of two-dimensional electron grid (antidot) structures. We develop a variational Wigner-Seitz model to study such periodic electron structures. We derive an analytical solution for the far-infrared (FIR) response, and obtain results in quantitative agreement with experiments. Our work provides not only an explanation for the recently observed FIR anomaly, but also a useful basis for further theoretical studies of collective properties of electron grid (antidot) structures.

We calculate the one-particle Green function of 2D fermions interacting via a long-range transverse gauge field. Its asymptotic low-energy behavior is found within the eikonal expansion which consistently sums the infrared divergent terms given by ‘‘maximally crossed diagrams.’’ Instead of power law corrections to Fermi liquid theory we observe a much stronger singularity which implies a more radical breakdown of Fermi liquid theory than the usual orthogonality catastrophe.

The influence of oxygen adsorption on a partly occupied spin-split surface state at Ni(111) has been studied by spin-resolved inverse photoemission. With increasing oxygen exposure the surface state shifts to higher energy, thereby becoming totally unoccupied and no longer contributing to the surface magnetic moment. Moreover, its exchange splitting of about 100 meV on the clean surface is reduced to less than 25 meV for the ordered p(2×2) oxygen overlayer, whereas the splitting of an sp bulk band transition remains unaffected. The data demonstrate on a microscopic level the oxygen-induced reduction of the magnetic moment at the surface of Ni(111).

We use experimental and calculated excitation spectra of bimetallic jellium films with widths of up to a few Fermi wavelengths to explore how excitations of a thin metal with internal density gradients evolve into surface plasmons of a three-dimensional layer. We find that the onset of 3D plasmons is mode specific, and sensitive to surface potentials, even for small surface wave vectors.

The nonlocal current response to an electric field characteristic of the superconducting state has been predicted to be observable in the paraconductive regime above the transition temperature ${\mathit{T}}_{\mathit{c}}$ over a length scale set by the correlation length for superconducting fluctuations, Ξ(T). A manifestation of this effect has been found in a multiterminal measurement of a square superconducting loop of characteristic size, L∼Ξ(T). The ratio of the voltages measured by two different sets of probes attached to the loop at different positions is observed to oscillate as a function of the flux threading the loop. This nonlocal effect is distinct from analogous phenomena associated with the coherent transport of electrons in mesoscopic structures.

We present an experiment designed to determine directly the symmetry of the pairing state in the cuprate superconductors. From the magnetic flux modulation of YBCO-Pb dc SQUIDs, we determine the spatial anisotropy of the phase of the order parameter in single crystals of YBCO. The experimental results are complicated by SQUID asymmetries and the trapping of magnetic vortices, but taken as a whole give rather strong evidence for a phase shift of π that is predicted for the ${\mathit{d}}_{\mathit{x}}^{2\mathrm{-}}$${\mathit{y}}^2$ pairing state. This is further corroborated by single junction modulation measurements.

A new scenario, based on crystallization of oppositely charged vortex-antivortex pairs into a 2D ionic crystal, is proposed for the transition in thin superconducting films with high pair density. We also discuss possible melting of this crystal and the emergence of dissipation. This model is also shown to apply to superfluid He films in cases where the energy to create a vortex is reduced due to interaction with the substrate.

In a recent experiment by Chen, Roesler, and Mochel, a new transition was found in the superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ film on a hydrogen surface, with a transition temperature below the Kosterlitz-Thouless transition temperature. We suggest that the intermediate phase between these two transitions is a lattice form by the superfluid vortices and antivortices. The transverse phonon mode of this lattice is identified with the ‘‘extra mode’’ detected in the third sound measurement.

We report measurements of the resistivity and the specific heat, performed as a function of temperature, magnetic field, and hydrostatic pressure on the antiferromagnetic (${\mathit{T}}_{\mathit{N}}$=14 K) heavy-fermion superconductor (${\mathit{T}}_{\mathit{c}}$=2 K) ${\mathrm{UPd}}_2$${\mathrm{Al}}_3$. Our results suggest a coexistence of two subsystems with more localized 5f states responsible for the magnetic properties and less localized states responsible for the superconducting properties. The latter are compatible with an order parameter of octagonal d-wave symmetry.

We have developed an algorithm for calculating the opening of base pairs in the double helix based on a modification of self-consistent phonon theory. The calculated results are in good agreement with experimental observation for both the fluctuational opening in the premelting regime and the critical behavior at the melting transition. We apply the algorithm to a localized structure, a model of the replicating fork, and find that the addition of two hot phonons added to local modes will lead to the separation of the last closed base pair and the advance of the fork. Several other combinations of hot phonons will also bring about separation and advance of the fork as needed in replication.

An experimental evidence for kinetic roughening in a micromodel of mountain ranges is presented. We have observed that during the watering of an initially smooth ridge made of a mixture of silica sand and earthy soil the surface evolves into a shape analogous to actual mountain profiles with self-affine geometry. For the exponents describing respectively the temporal and the spatial scaling of the surface width β≊0.9 and α=0.78±0.05 have been obtained. The latter value is in very good agreement with α=0.8±0.1 we have calculated for genuine transect profiles.

We investigate the magnetized Bose gas at temperatures above pair threshold. New magnetization laws are obtained for a wide range of field strengths, and the gas is shown to exhibit the Meissner effect. Some related results for the Fermi gas, a relativistic paramagnet, are also discussed.

We study the trajectories followed by a particle weakly perturbed by noise, when escaping from the domain of attraction of a stable fixed point. If the particle’s stationary distribution lacks detailed balance, a focus may occur along the most probable exit path, leading to a breakdown of symmetry (if present). The exit trajectory bifurcates, and the exit location distribution may become ‘‘skewed’’ (non-Gaussian). The weak-noise asymptotics of the mean escape time are also affected. Our methods extend to the study of skewed exit location distributions in stochastic models without symmetry.

We analyze the axial vector coupling of the constituent quark in the large-${\mathit{N}}_{\mathit{c}}$ limit and point out mechanisms which yield 1-${\mathit{g}}_{\mathit{A}}$∼${\mathit{N}}_{\mathit{c}}^0$.

The decay ${\mathrm{\tau }}^{\mathrm{-}}$→${\mathrm{\pi }}^{\mathrm{-}}$${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$2${\mathrm{\pi }}^0$${\nu }_{\mathrm{\tau }}$ has been observed in ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ annihilation using the CLEO II detector at the Cornell Electron Storage Ring. In a data sample collected at √s ∼10.6 GeV, 668±38 decay candidates have been identified by exclusively reconstructing two ${\mathrm{\pi }}^0$’s accompanying three charged particles, which are assumed to be pions. Normalizing to the number of τ pairs detected with one charged particle recoiling against three charged particles, this yields a branching ratio of ${\mathit{B}}_{3\mathrm{\pi }2\mathrm{\pi }}^0$=(0.48±0.04±0.04)%. A signal of 430±33 events for the decay ${\mathrm{\tau }}^{\mathrm{-}}$→${\mathrm{\pi }}^{\mathrm{-}}$ω${\mathrm{\pi }}^0$${\nu }_{\mathrm{\tau }}$ has also been observed, corresponding to a branching ratio of ${\mathit{B}}_{\mathrm{\pi }\mathrm{\omega }\mathrm{\pi }}^0$=(0.39±0.04±0.04)%.

Inclusive double-differential cross sections for 500-MeV pions are presented for C(${\mathrm{\pi }}^{\pm }$,${\mathrm{\pi }}^{\pm }$) at ${\mathrm{\theta }}_{\mathrm{lab}}$ of 30 °, 40 °, 50 °, 70 °, and 90 °; and for C(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$) at 110 °. We compare the 50 ° and 70 ° data with C(e,e’) data at nearly the same momentum transfer. These spectra from very different probes are more similar than expected from an intranuclear cascade calculation, which includes the strong rescattering of pions that have energies near 180 MeV. Agreement of the calculated spectra and the pion data is improved if the nucleus is assumed to be nearly transparent to these pions.

The superdeformed (SD) structure of ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ has been studied using the Eurogam gamma-ray spectrometer and three new SD bands have been discovered. An interaction is observed between two of the SD bands caused by the near degeneracy of two levels. This is the first observation of accidental degeneracy between SD states. The interaction strength is determined to be 11 keV and evidence for crosstalk between the bands is observed. The absolute energy difference between two SD states in the second minimum has been accurately measured and the relative spins and parities of the two bands have been fixed.