Two superconducting phases, ${\mathrm{Tl}}_2$${\mathrm{Ca}}_2$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10+\mathrm{\delta }}$ (2223) and ${\mathrm{Tl}}_2$${\mathrm{Ca}}_1$${\mathrm{Ba}}_2$${\mathrm{Cu}}_2$${)}_{8+\mathrm{\delta }}$ (2122), both with onset ${\mathrm{T}}_{\mathrm{c}}$ near 120 K and zero resistivity at 100 K, have been isolated from samples in the Tl-Ca-Ba-Cu-O system. The new 2223 superconductor has a 5.40×5.40×36.25-A${\mathrm{̊}}^3$ pseudotetragonal unit cell. The 2122 superconductor, which appears to be structurally related to ${\mathrm{Bi}}_2$${\mathrm{CaSr}}_2$${\mathrm{Cu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$, has a 5.44×5.44×29.55-A${\mathrm{̊}}^3$ pseudotetragonal subcell. The 2223 phase is probably related to 2122 by the addition of extra calcium and copper layers.

The band structure for body-centered tetragonal ${\mathrm{CaBi}}_2$${\mathrm{Sr}}_2$${\mathrm{Cu}}_2$${\mathrm{O}}_8$ has been calculated in the local-density–functional approach by the linearized muffin-tin–orbital method with the atomic-sphere approximation. This is the undistorted, stoichiometric parent compound to the recently reported 84-K superconductor. The main band features at the Fermi level include a pair of nearly half-filled two-dimensional Cu-O 3d-2p bands similar to those found in the previous Cu-O planar superconductors as well as a pair of slightly filled Bi 6p bands that provide additional carriers in the Bi-O planes.

The electronic structure of the new Bi-based high-temperature superconductor, with $T_c$ onsets above 110 K, is shown to be altered considerably from that of the other cuprate superconductors by the presence of Bi. There are Bi-O bands which cross the Fermi level, and the two-dimensional character of the bands is even greater than that of previous cuprates. Like the other cuprates, band critical points occur at the Fermi level.

We show that planar ${\mathrm{CuO}}_2$ clusters with strong repulsive Coulomb interactions can exhibit an effective attractive pairing interaction. This interaction arises from a disruption of the local lattice charge distribution produced when a hole is added and occurs for a wide range of parameter values, in the region where both the on-site Cu repulsion and the nearest-neighbor Cu-O repulsion are appreciable. A signature of this mechanism is that the occupation of Cu sites decreases as the system is doped. We suggest that this effective attractive interaction is responsible for high-$T_c$ superconductivity in oxides.

The dynamic conductivity of one-dimensional hopping systems with aperiodically distributed transition rates is studied. The low-frequency behavior is shown to be regular or singular depending on the specific substitution which generates the aperiodicity. Explicit formulas are given for three cases with different spectral measures of the transition-rate sequences. We give general high-frequency expansions that are valid whenever the correlation functions exist. A numerical calculation of the conductivity in the range of intermediate frequencies by a decimation procedure is also included.

The deformations of a 2D vortex lattice pinned by a random potential are studied by a molecular-dynamics annealing method. All but very weak potentials produce a highly defective lattice, consisting of trapped lattice regions separated by channels in which the vortices flow plastically. It is argued that this type of deformation is the cause of the observed restricted applicability of collective pinning theory.

Topological entanglements play an important role in the physical properties, such as viscosity, of macromolecular structures. We investigate the likelihood of the appearance of entanglements in the bond percolation problem. We show that below the percolation threshold ${\mathrm{p}}_{\mathrm{c}}$ (but extremely close to it) there exists an entanglement threshold ${\mathrm{p}}_{\mathrm{e}}$. Between ${\mathrm{p}}_{\mathrm{e}}$ and ${\mathrm{p}}_{\mathrm{c}}$, there exists an infinite spanning group of interlocked (linked) clusters. The achieved numerical resolution of ${\mathrm{p}}_{\mathrm{c}}$-${\mathrm{p}}_{\mathrm{e}}$=(1.8±0.4)×${10}^{\mathrm{-}7}$ required averaging over an extremely large number of configurations.

For a given lattice spin or gauge theory an associated correlated bond or plaquette percolation process is constructed. It is conjectured to reproduce the universal scaling behavior of the original model. Different field theories lead to different cluster weights generalizing a result by Fortuin and Kasteleyn for Potts models. The new representation lends itself to the design of Monte Carlo algorithms with reduced critical slowing down.

By considering Symanzik’s improvement program of the continuum limit of scalar lattice field theory as a tool to make contact between the perturbative renormalization and Wilson’s theory, we show the nonperturbative nature of the renormalization. As a consequence we justify the conjecture of Parisi that the critical exponents may be estimated by field-theoretical methods without recourse to the ε expansion.

We show that under rather general assumptions, the ratio of the masses of the $2^{++}$ tensor and the $0^{++}$ scalar glueballs in lattice gauge theory can be directly expressed in terms of two ground-state correlation coefficients. A simple variational estimate of these two coefficients in the case of SU(3) and SU(6) suggests that although these two masses remian highly degenerate in the intermediate-coupling regime, the ratio M${(2\mathrm{}}^{++}$)/M${(0\mathrm{}}^{++}$) never drops below 1 for coupling up to 1/${\mathrm{Ng}}^2$≊0.4, which is well beyond the expected scaling region.

Data on polarized lepton-proton scattering are shown to give no clear conclusion on the spin content of the proton. We argue that errors have been underestimated, specifically those arising from the uncertainty of the extrapolation to infinite energy (x→0). Estimates of the spin content are sensitive to such uncertainty and possible ways of surmounting this problem are discussed.

The E1 capture cross section for the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(α,γ${)}^{16}$O to the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ground state has been measured for $E_{\mathrm{c}.\mathrm{m}.\mathrm{}=1.29\mathrm{}–}$3.00 MeV. A γ-ray–recoil-particle coincidence technique has been used to obtain essentially background-free reaction yields. A three-level R-matrix analysis of the E1 S factor leads to an allowed range for $S_{E1}$ at 300 keV of 0.00–0.14 MeV b. A model-dependent R-matrix analysis and a hybrid R-matrix analysis result in values of 0.14 and 0.08 MeV b, respectively, for $S_{E1}$(300).

The sign of the emission angle for nonequilibrium intermediate-mass fragments was determined from the circular polarization of coincident γ rays for ${}_{}{}^{14}{}_{}{}^{}\mathrm{induced}$ reactions on ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ at E/A=35 MeV. Positive polarizations, $P_{\gamma }$≤0.3–0.4, are observed for fragments with 3≤Z≤6, consistent with fragment emission after deflection by the attractive nuclear mean field to negative emission angles. These polarizations are small compared to the trends established for nonequilibrium light particles and the expectations of simple dynamical production mechanisms.

Double-charge-exchange reactions induced by pions furnish a direct means of detecting nucleon-nucleon correlations in nuclei. For the particular case of double isobaric analog transitions the effect of correlations is easily isolated and quite strong. We show that the magnitudes of the double-charge-exchange cross sections for the isotopes ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}$, recently measured at low energies, can be explained well by our taking account of the position correlations of the valence neutrons in the respective ground states.

The optical absorption profile of an atom-surface vibrational bond is studied. From Markovian relaxation theory it follows that the line shape is a Lorentzian around the adsorbate resonance frequency ${\mathrm{\omega }}_0$. Dispersion relations for crystals have a fairly small cutoff frequency ${\mathrm{\omega }}_{\mathrm{D}}$, which prohibits the use of such a simple theory. We calculated the spectral profile with finite–memory-time reservoir theory, and we found that the modified Lorentzian vanishes above ${\mathrm{\omega }}_{\mathrm{D}}$. Also a new spectral line at ${\mathrm{\omega }}_0$+${\mathrm{\omega }}_{\mathrm{D}}$ is predicted, which disappears in the Markovian limit. The physical origin of the new line is explained.

Photoelectron spectra and zero-volt electron scans were measured following synchrotron-radiation excitation of argon, to elucidate the photon energy range between threshold and the Cooper-minimum region of the Ar 3s photoline. A number of the ‘‘correlation satellite’’ lines show a dramatic increase of fractional intensity, yielding a total of about forty observed photolines at threshold. This effect is interpreted as arising from strong interchannel coupling near threshold, yielding high–angular-momentum ionic states otherwise inaccessible. The distinction between ‘‘intrinsic’’ correlation effects due to discrete states and ‘‘dynamic’’ correlations arising through the photoemission process is emphasized.

We have excited and detected an atomic electron wave packet that is localized in the polar and azimuthal angles. The wave packet is formed through the coherent superposition of Rydberg states of atomic sodium. The superposition is achieved by short-pulse optical excitation of the atom in the presence of a strong rf field. The wave packet is detected by dc field ionization. The behavior of this wave packet in a strong dc field is much different from that of an eigenstate. This behavior agrees well with a simple classical model.

The existence of guided and surface electron drift waves in magnetoactive plasmas is demonstrated. The conditions for each of these modes to exist are found It is shown that the surface mode is unstable if the gradients of the plasma density and of the externally applied dc magnetic field are parallel within a localized region of the plasma.

Counter injection into ASDEX leads to good particle, momentum, and also energy confinement with ${\tau }_E$=80 ms at 1 MW (43 ms for co-injection). The improved confinement develops gradually during the heating phase and correlates with a simultaneous peaking of the density profile. The ion heat transport has to be reduced for a consistent transport analysis, in agreement with theoretical expectations. The sawtooth instability flattens the density profile and transiently reduces the energy content.

Flute-mode turbulence has a forward spectral cascade unlike the case of drift-wave turbulence. Therefore the linear flute instability may be reduced by this energy cascading toward large wave numbers. As a consequence of three-wave cascade processes derivable from model equations including the effects of density gradient and finite ion Larmor radius the formation of zonal flows in flute mode turbulence is predicted.