The sample-to-sample fluctuations in the critical current of a disordered Josesphson junction are analyzed by means of a transmission-matrix formalism. If the junction becomes small compared to the superconducting coherence length, the fluctuations at T=0 become of order e${\mathrm{\Delta }}_0$/ħ, dependent only on the energy gap ${\mathrm{\Delta }}_0$ of the bulk superconductors and independent of junction length or mean free path. This universal limit is reached in weak links formed from point contacts or microbridges.

We derive a variational replica-symmetry-breaking theory for the effect of random impurities on two- and three-dimensional vortex lattices. We find that the translational correlation functions decay as stretched exponentials with exponents which seem to be in good agreement with experiments. We predict, in the absence of dislocations, long-range orientational order in three and two dimensions.

We demonstrate, by direct use of the asymptotic Green’s functions of Korepin and Ren, that the one-dimensional repulsive U Hubbard model has the property of ‘‘confinement,’’ in that weak interchain coupling does not cause coherent particle motion in the transverse direction at absolute zero. Implications for real one-dimensional systems and for the two-dimensional Hubbard model are discussed.

We show how to construct a complete set of eigenstates of the Hamiltonian of the one-dimensional Hubbard model on a finite lattice of even length L. This is done by using the nested Bethe ansatz and the SO(4) symmetry of the model.

One-dimensional metals have a particular symmetry associated with the discrete structure of the Fermi surface: separate charge conservation in low-energy-scattering processes for particles near the left and right Fermi points, respectively. The field-theoretical renormalization group allows for an efficient exploitation of the Ward identities following from this symmetry. As a first application we prove that the β function of the Luttinger model vanishes identically. The same symmetry ensures the finiteness of the compressibility, thus making possible the existence of stable metallic phases with anomalous dimensions in d=1.

We investigate the behavior of the thermal conductivity κ(H) of both twinned and untwinned single crystals of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ in a magnetic field. Remanant field data are examined in the framework of the Bean critical state model and thermally activated flux creep. In-field data are shown to depart from conventional superconductor models. The κ(H) profie is fitted by a phenomenological form and is suggested to originate from Bloch wave travel of phonons through a vortex array which becomes more regular as the field increases.

The femtosecond dynamics of reflection and transmission spectra of a ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ film have been studied in the wavelength range 620–680 nm at initial temperatures ${\mathit{T}}_0$ both above and below the critical temperature ${\mathit{T}}_{\mathit{c}}$. A difference has been found to exist between the spectral responses for ${\mathit{T}}_0$<${\mathit{T}}_{\mathit{c}}$ and ${\mathit{T}}_0$>${\mathit{T}}_{\mathit{c}}$, which can be attributed to the presence of an energy gap in the spectrum at ${\mathit{T}}_0$<${\mathit{T}}_{\mathit{c}}$. Based on the experimental data, the electron-phonon-interaction parameter λ〈${\mathrm{\omega }}^2$〉 has been estimated as (4±2)×${10}^2$ ${\mathrm{meV}}^2$.

A recent theory of Raman scattering in the Hubbard model predicts scatteirng of ${\mathit{A}}_2$ symmetry arising from chiral spin fluctuations. In the doped planar cuprates, chiral spin fluctuations have been speculated to play a central role in establishing the normal-state properties. In addition to spin fluctuation scattering in the ${\mathit{B}}_1$, ${\mathit{A}}_1$, and ${\mathit{B}}_2$ symmetries, we report here the direct observation of dynamic chiral spin fluctuations, appearing in the inelastically scattered light of ${\mathit{A}}_2$ symmetry. In ${\mathrm{Gd}}_2$${\mathrm{CuO}}_4$, the ${\mathit{A}}_2$ scattering broadly peaks near 4700 ${\mathrm{cm}}^{\mathrm{-}1}$ (∼5J) and extends beyond 8000 ${\mathrm{cm}}^{\mathrm{-}1}$ (1 eV).

A colloidal crystal formed by spherical latex particles possessing intrinsic optical anisotropy is studied by light scattering. Dynamic depolarized scattering gives information about the ‘‘self-motion’’ of particles within the crystal. It is found that the particles behave as Brownian harmonic oscillators with a finite escape time from the potential well. The mean-square dispalcement of the particle within the crystal is obtained from the experimental data. It is also found that the short time rotational diffusion rate in the colloidal crystal is larger than in the dilute suspension.

We study how a Cantor spectrum, its level statistics, and corresponding dynamics are affected by the onset of classical chaos. While the spectrum undergoes visible changes, its level spacing distribution follows an inverse power law p(s)∼${\mathit{s}}^{\mathrm{-}3/2}$ on small scales. We find a crossover which is manifested in the time domain by two diffusive regimes characterized by a classical and a quantum-mechanical diffusion coefficient. In the strong quantum limit we show by means of a transformation that the spectrum is governed by the IintegrableP Harper equation, even if the classical phase space is strongly chaotic.

We present a generalization of the thin-wall formalism to calculate the evolution of true-vacuum bubbles in ‘‘extended’’ inflaton. For inflation quartic couplings of the order M/${\mathit{M}}_{\mathrm{Pl}}$, gravity will lead to the recollapse of bubbles during most of the extended-inflation period thereby altering the bubble size distribution. The completion of the phase transition will proceed through tiny bubbles satisfying homogeneity constraints of the microwave background for arbitrary values of ω. Thus, it is possible to construct models that agree with experiments even for the original version of extended inflation.

We demonstrate that U(1) charge is quantized in the presence of an Alice string in 3+1 dimensions, and show that spontaneously broken gauge theories containing such strings necessarily possess magnetic monopoles. The string and monopole quantization conditions are compared, and we make a few brief comments concerning their modification in a θ vacuum.

It is known that much of the structure of string theory can be derived from three-dimensional topological field theory and gravity. We show here that, at least for simple topologies, the string diffeomorphism ghosts can also be explained in terms of three-dimensional physics.

We evaluate the cross section of multiparticle production in weak-coupling λ${\mathit{\phi }}^4$ theory at high energies. By means of dispersion relations the problem is reduced to the long-standing problem of summation of perturbative series at low energies. Applying the technique and insight gained in the latter case we derive the total cross section of Higgs-boson production. The cross section is dominated by low-order terms and is small at all energies. The conclusions are in drastic variance with the tree approximation to the same cross section.

We studied ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ ${\mathrm{\beta }}^{+}$ decays using a mass separated ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ beam and a proton telescope with 16-keV resolution. Delayed p’s were detected in coincidence with γ’s to identify p decays of ${}_{}{}^{37}{}_{}{}^{}\mathrm{K}$ daughter levels to excited states of ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$. We observed 43 previously undetected proton groups, yielding an integrated B(GT) twice as large as that observed previously. Although our result increases the efficiency of the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$ detector for counting solar ν’s by 6%, its main effect is to reduce uncertainties in this efficiency arising from discrepancies between previous ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ β decay and ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) results.

The measured Gamow-Teller strength in ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ ${\mathrm{\beta }}^{+}$ decay, which has an unusually high energy release, differs significantly from shell-model predictions and also from the analogous strength inferred from the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) reaction. This calls into question the claim, based primarily on shell-model analyses of low-energy-release β-decay rates and (p,n) cross sections, that ${\mathit{g}}_{\mathit{A}}$ is significantly renormalized in complex nuclei.

Co and Fe isotopes have been identified in thermal-neutron-induced fission of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$. The yields of the very neutron-rich isotopes ${}_{}{}^{69}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{68}{}_{}{}^{}\mathrm{Co}$, and ${}_{}{}^{68}{}_{}{}^{}\mathrm{Fe}$ were measured and their β-decay half-lives were obtained from time correlations between detection of the selected isotopes and of the β particles from their decay.

Exact results on the time evolution of the density matrix and the Wigner function for an oscillator with time-dependent frequency are given. Explicit time dependence is given for the case of linear sweep of the restoring force. Such a sweep is shown to generate states of the oscillator with remarkable nonclassical properties such as squeezing and sub-Poissonian character.

We report the first observation of an asymmetric autoionizinglike line shape in the ionization of atomic Na due to laser-induced continuum structure. The results are in very good agreement with a theoretical time-dependent analysis employing independently calculated atomic parameters combined with the instrumental parameters of the experiment.

We report the observation of a structure in the ionization spectrum of sodium, induced by a strong radiation field embedding the 5s ${}_{}{}^2{}_{}{}^{}$${\mathit{S}}_{1/2}$ state into the continuum. The structure, probed by single-photon ionization, shows a marked asymmetry, typical of a laser-induced continuum structure.