Recent experiments in charge-density-wave systems suggest that thermally activated phase slip is responsible for current flow. We present a quantitative theory that explains the nonlinear current-voltage relationship.

Tunnel junctions formed between tungsten wires display very large zero-bias conductance peaks characteristic of Kondo-type magnetic scattering of tunneling electrons. No electron correlation effects are seen despite the fact that the system appears to be below the Kondo temperature. Time-dependent changes in the tunnel conductance are identified with the scattering behavior of a single local magnetic moment. This behavior can be switched reversibly by adjusting the stress in the junction.

We consider the van der Waals interaction for systems carrying a nonzero current. We show that in simple cases, such as two parallel wires or sheets, the van der Waals attraction increases quadratically, with the difference between the currents in the two subsystems. This implies a nonzero current drag at zero temperature, a new effect that could be detected experimentally.

The Hall coefficient in the strongly correlated Fermi-liquid phase of the t-J model is studied for moderate hole concentrations. We find that the quasiparticle self-energy is strongly k dependent due to gauge-field interactions. It leads to corrections to the Fermi-surface curvature and to enhancement of the quasiparticle lifetime in the holelike region. We show that a systematic treatment of the strong local correlations to next to leading order in 1/N is sufficient to give rise to a sign change in the Hall coefficient. This effect occurs near 0.20 doping for J/t=0.2 and may be relevant to the high-${\mathit{T}}_{\mathit{c}}$ materials.

The spectral density A(k,ω) for the three-band Hubbard model is calculated using quantum Monte Carlo data. The states closest to the Fermi energy are related to the Zhang-Rice singlet and exhibit a bandlike behavior for a doping δ=0.25. At this hole concentration we find quantitative agreement for both the Fermi velocity and the location of the Fermi surface, when compared with angle-resolved-photoemission data.

We report the low-temperature dynamics of a diluted Ising antiferromagnet (${\mathrm{Fe}}_{0.46}$${\mathrm{Zn}}_{0.54}$${\mathrm{F}}_2$) over a wide range of magnetic fields. By measuring the magnetization through a number of cooling protocols, we deduce the density of antiferromagnetic domain walls, which can be compared with predictions of the random-field Ising model (RFIM). In both magnetization-relaxation and field-cycling experiments, we find a region of the (H,T) phase diagram in which the dynamic behavior is consistent with the RFIM, as well as a theoretically unexpected region of frozen dynamics.

Fast numerical methods are used to solve the equations for periodically rotating spiral waves in excitable media, and the associated eigenvalue problem for the stability of these waves. Both equally and singly diffusive media are treated. Rotating-wave solutions are found to be discretely selected by the system and an isolated, complex-conjugate pair of eigenmodes is shown to cause instability of these waves. The instability arises at the point of zero curvature on the spiral interface and results in wavelike disturbances which propagate from this point along the interface.

A new method is presented that allows the determination of dynamical properties of disordered spin systems avoiding finite-size effects. The method is based on exact dynamical mean-field equations for the infinite large system. The resulting single-spin dynamics is solved by Monte Carlo simulations. We outline the formalism for the parallel dynamics of a fully connected model with random couplings. The decay of remanent magnetization of the model is studied. We find a power-law decay: m(t)-m(∞)∝${\mathit{t}}^{\mathrm{-}\mathit{a}}$, with a=0.474 and m(∞)=0.184 for the infinite system.

A specific crystalline order, involving the Fibonacci series, had until now only been observed in plants (phyllotaxis). Here, these patterns are obtained both in a physics laboratory experiment and in a numerical simulation. They arise from self-organization in an iterative process. They are selected depending on only one parameter describing the successive appearance of new elements, and on initial conditions. The ordering is explained as due to the system’s trend to avoid rational (periodic) organization, thus leading to a convergence towards the golden mean.

We study the time evolution of a wave packet in a rapidly varying (in time) random potential. We find that the wave function becomes ‘‘multifractal,’’ i.e., that an infinite number of exponents is needed to describe its evolution. The width of the packet is found to increase as √t , i.e., diffusively. The evolution of the center of mass is compatible with a subdiffusive ${\mathit{t}}^{1/4}$ law.

We investigate the reaction kinetics for systems in which the dynamics of the particles is governed by a Langevin equation with negligible damping, and we find the expressions for the survival probability, residual concentrations, and reaction rates. We discover that the integral in time of the reaction front for d=1 is ${\mathit{t}}^{1\mathrm{-}\mathrm{\beta }}$ exp(-‖x‖/${\mathit{t}}^{\mathrm{\alpha }}$) for both the low- and high-damping limits, and we estimate the exponents α and β in each case.

We study the q-deformed su(2) spin network as a three-dimensional quantum gravity model. We show that in the semiclassical continuum limit the Turaev-Viro invariant obtained recently defines a naturally regularized path integral a` la Ponzano and Regge, in which a contribution from the cosmological term is effectively included. The regularization-dependent cosmological constant is found to be 4${\mathrm{\pi }}^2$/${\mathit{k}}^2$+O(${\mathit{k}}^{\mathrm{-}4}$), where ${\mathit{q}}^{2\mathit{k}}$=1. We also discuss the relation to the Euclidean Chern-Simons-Witten gravity in three dimensions.

A phenomenological model of gamma-ray-burst spectra is used to calculate the statistics of gamma-ray bursts originating at cosmological distances. A model of bursters with no source evolution in a ${\mathit{q}}_0$=1/2 Friedmann cosmology is in accord with recent observations of the differential V/${\mathit{V}}_{\max }$ distribution. The data are best fitted with an average peak burst luminosity of 4(±2)×${10}^{51}$ ergs ${\mathrm{s}}^{\mathrm{-}1}$ and a present-day source emissivity of 940±440 bursts/(${10}^{10}$ yr) ${\mathrm{Mpc}}^3$. A spectral test of the cosmological hypothesis is proposed.

In the standard electroweak theory, if the Higgs boson mass is comparable with the weak scale, the electroweak transition is weakly first order, and proceeds via bubble nucleation. It is shown that the Universe supercools beyond the point where phase equilibrium is possible. When true-vacuum bubbles nucleate, they expand at velocities of the order of the speed of light until they fill the Universe. These considerations are important for the recently proposed electroweak baryogenesis mechanisms.

We construct a canonical formulation of the self-dual Yang-Mills system formulated in the gauge-invariant group-valued J fields and derive their Hamiltonian and the quadratic algebras of the fundamental Dirac brackets. We also show that the quadratic algebras satisfy Jacobi identities and their structure matrices satisfy modified Yang-Baxter equations. From these quadratic algebras, we construct Kac-Moody-like and Virasoro-like algebras. We also discuss their related symmetries, involutive conserved quantities, and hierarchies of nonlinear and linear equations.

A pure (2+1)-dimensional classical Yang-Mills system is started with a sine-wave nonuniformity in space. One of the potentials soon develops, as a function of position, into an approximate fractal with fractal dimension 1.40.

The left-handedness of the b quark weak couplings has not yet been tested experimentally. We present an SU(2${)}_{\mathit{L}}$×SU(2${)}_{\mathit{R}}$×U(1) model with purely right-handed b decay couplings. We show that the model is consistent with the quite severe existing experimental constraints from B decays, from ${\mathit{B}}^{0\mathrm{-}}$B¯ ${}_{}{}^0{}_{}{}^{}$ mixing, from the neutral K mass difference, and from CP violation in the kaon system. We point out a difficulty in distinguishing our scheme from the standard model in semileptonic B decays.

The existence of empirical tests for the validity of chiral perturbation theory in the analysis of nonleptonic kaon decay is pointed out in the context of K→2π,3π processes. Comparison with existing data reveals good agreement with the chiral constraints.

It is shown that, in models in which neutral-Higgs-boson exchange mediates CP violation, T and P odd electron-nucleon interactions would arise at a measurable level. In two-doublet models for large tanβ (∼30) the contribution of these interactions to the electric dipole moments of large atoms can exceed the contribution of the electron electric dipole.

Superficial violation of the Pauli principle due to the possible substructure of electrons is discussed in composite models of quarks and leptons. The ratio of the Pauli forbidden atomic transition to the allowed one is estimated to be of order ${10}^{\mathrm{-}50}$–${10}^{\mathrm{-}44}$ for heavy atoms if the size of the electron is of order ${10}^{\mathrm{-}17}$ cm.