It is shown by dielectric resonance absorption at 60 GHz that there is a linear coupling of the electric field to the ground state of effective mass acceptors in Si reflecting the lower ${\mathit{T}}_{\mathit{d}}$ symmetry in the central portion of the ground-state wave function. The coupling increases strongly with increasing binding energy from B to In, i.e., with decreasing Bohr radius of the acceptor. An unexpected nonlinear Zeeman splitting is observed the magnitude of which also increases from B to In. For all acceptors a central fine structure is found which correlates with the homogeneous linewidth.

The problem of calculating the zero-temperature mean conductance 〈c〉 of a disordered thick metallic wire coupled at both ends to ideal leads is formulated as a diffusion problem on a Riemannian symmetric superspace G/K (Efetov). The problem is solved exactly by Fourier transforming the diffusion kernel. Although the solution agrees with known results for the case of orthogonal and unitary symmetry, it has the surprising feature that 〈c〉 never falls below the minimum value of ${\mathit{e}}^2$/2h for long wires with symplectic symmetry, in leading order of the expansion around the metallic and thick limit.

Extremely well-resolved Si 2p core-level spectra have been obtained from the clean Si(001) surface. Spectra from the cold c(4×2) and the RT 2×1 surfaces are very similar, implying that the local structure of the two reconstructions is the same. Shifted components originating from both up and down atoms of asymmetric dimers, as well as second-layer atoms, are identified. The split of ∼0.55 eV between the two dimer-atom components points to a substantial charge transfer within the dimers. We find no support for the recently proposed crystal-field splitting of the surface components.

We observe new transport effects in lateral quantum dots where zero-dimensional (0D) states and single electron charging coexist. In linear transport we see coherent resonant tunneling, described by a Landauer formula despite the many-body charging interaction. In the nonlinear regime, Coulomb oscillations of a quantum dot with about 25 electrons show structure due to 0D excited states as the bias voltage increases, and the current-voltage characteristic has a double-staircase shape.

It is shown that appropriately shaped smooth pulses of an external oscillating force lead to population transfer in a bistable quantum system on a time scale that can be orders of magnitude shorter than the bare tunneling time. Those pulse shapes for which this phenomenon is achieved can accurately be determined from a tunneling functional ${\mathrm{\Delta }}_{\mathit{T}}$ which is constructed explicitly.

We demonstrate for the nearly half-filled Holstein-Hubbard model that the presence of antiferomagnetic spin correlations can cause polaronic carrier self-localization, and hence a strongly anharmonic lattice potential, already at moderate electron-phonon coupling strengths λ∼0.2–0.4, up to substantial hole dopant concentrations ${\mathit{c}}_{\mathit{h}}$∼(20–30)%. The results are compared to recent observations of anharmonicity in the apical oxygen c-axis motion of cuprate superconductors.

Temperature and magnetic-field-dependent measurements of the longitudinal ${\mathit{R}}_{\mathit{x}\mathit{x}}$ and transverse ${\mathit{R}}_{\mathit{x}\mathit{y}}$ resistance of amorphous indium oxide thin-film superconductors reveal the presence of distinct insulating phases for sufficiently high disorder and/or magnetic field. For field-swept transitions at fixed disorder and low temperatures there is a critical field where ${\mathit{R}}_{\mathit{x}\mathit{x}}$ diverges and the superconductor is transformed into a Bose-glass insulator with localized Cooper pairs. At higher fields there is a second critical field where ${\mathit{R}}_{\mathit{x}\mathit{y}}$ appears to diverge, the pairs unbind, and localized single electrons characterizing a Fermi-glass insulator dominate.

We study a class of Hubbard models in which the corresponding single-electron ground states have bulk degeneracy. We prove that the ground states of the models exhibit ferromagnetism when the electron filling factor is not more than and sufficiently close to ${\mathrm{\rho }}_0$=‖V‖/2‖Λ‖ (where ‖V‖ is the dimension of degeneracy and ‖Λ‖ is the number of sites), and exhibit paramagnetism when the filling factor is sufficiently small. This is the first time that a three-dimensional itinerant-electron system is proved to exhibit ferromagnetism in a finite range of the electron filling factor.

An unexpected resonant enhancement in x-ray diffraction occurs at a forbidden reflection in the antiferromagnetic hematite. This fifty-fold increase in the diffracted signal, 10 eV below the iron K edge, exhibits a rotation in the x-ray polarization and a 60° azimuthal symmetry as the crystal is rotated about the reflection vector. The effect is explained to result from electronic quadrupole transitions in the anomalous scattering from iron and demonstrates that diffraction can be a sensitive probe of the electronic environment at specific atomic sites in the crystal.

We study a population of interacting species, described by the replicator model well established in theoretical biology. Using methods of statistical physics we present an exact steady-state solution to the model as a function of the population’s cooperation pressure u when the number of species is large and the interactions are taken as random. When u is lowered to a critical value ${\mathit{u}}_{\mathit{c}}$, the solution becomes unstable. This phase transition manifests itself by a 1/f behavior in the power spectrum of the system’s response against weak external noise.

We propose an experimental realization of cryptographic-key-sharing scheme exploiting quantum correlations between pair photons. Our experimental setup consists of an external source of correlated photon pairs which propagate to two widely separated unbalanced Mach-Zehnder interferometers. The probability of detection of photon pairs in any two outputs of the interferometers can be fully modulated by phase plates in either interferometer.

The complete sequence of 1060 eigenmodes with frequencies between 0.75 and 17.5 GHz of a quasi-two-dimensional superconducting microwave resonator shaped like a quarter of a stadium billiard with a Q value of Q≊${10}^{5–}$${10}^7$ was measured for the first time. The semiclassical analysis is in good agreement with the experimental data, and provides a new scheme for the statistical analysis and comparison with predictions based on the Gaussian orthogonal ensemble.

We present a set of equations that determine (with certain qualifications) what is (i) a complete canonical set of gauge-invariant variables for Yang-Mills (YM) theory that generalize Faraday’s electric lines of force and (ii) a complete canonical set of the diffeomorphism and gauge invariant observables for general relativity (GR). Both results come from solving the Hamilton-Jacobi version of the constraint equations: the Gauss law constraints of YM theory and the Gauss law and diffeomorphism constraint of GR in the Ashtekar formalism. These results are local in physical space as well as in phase space.

We examine the dynamics of the electroweak phase transition in the early Universe. For Higgs boson masses in the range 57≤${\mathit{m}}_{\mathit{H}}$≤150 GeV and top quark masses less than 200 GeV, regions of symmetric and asymmetric vacuum coexist to below the critical temperature, due to efficient thermal nucleation of subcritical fluctuations of the asymmetric phase within the symmetric phase. We propose that the transition to the asymmetric vacuum is completed by percolation of these fluctuations. Our results are relevant to scenarios of baryogenesis that invoke a weakly first-order electroweak transition.

Utilizing results on the cosmology of anomalous discrete symmetries we show that models of spontaneous CP violation can in principle avoid the domain wall problem. A small but nonzero ${\mathrm{\theta }}_{\mathrm{QCD}}$ explicitly breaks CP and can lift the degeneracy of the two CP conjugate vacua, so the domain walls become unstable, but can survive to cosmologically interesting epochs. We explore this in the context of a two-Higgs-doublet model. In this context, we show that axion solutions of the strong CP problem cannot be implemented without further extensions of the Higgs sector or other new physics.

We apply methods developed by Lovelace, Lipatov, and Kirschner to evaluate the leading Regge trajectories α(t) with the quantum numbers of nonexotic quark-antiquark mesons at ${\mathit{N}}_{\mathit{c}}$=∞ in the limit t→-∞ where renormalization-group-improved perturbation theory should be valid. We discuss the compatibility of nonlinear trajectories with narrow-resonance approximations.

We consider a renormalizable gauge-Higgs theory with chiral fermion content, in which gauge current anomalies are canceled between fermion multiplets with very different mass scales. We argue that this splitting of the anomaly cancelation can enchance certain low energy scattering amplitudes. In particular, we exhibit a logarithmic enhancement in the two-loop correction to the magnetic moment of massive neutrinos in a simplified SU(2)×U(1) version of the standard electroweak model. As an example of non-anomaly-related enhancements, we also exhibit a contribution to the anomalous magnetic moment of the W ${}_{}{}^{\pm }{}_{}{}^{}$.

We apply the optimization procedure based on the principle of minimal sesitivity to the third-order calculation of ${\mathit{R}}_{\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$. The effective couplant remains finite, freezing to a value ${\mathrm{\alpha }}_{\mathit{s}}$/π=0.26 at low energies. Using Poggio-Quinn-Weinberg smearing we find good agreement between theory and experiment right down to zero energy.

All available data indicate a surplus of baryon states over meson states for energies greater than about 1.5 GeV. Since hadron-scale string theory suggests that their number should become equal with increasing energy, it has recently been proposed that there must exist exotic mesons with masses just above 1.7 GeV in order to fill the deficit. We demonstrate that a stringlike picture is actually consistent with the present numbers of baryon and meson states, and in fact predicts regular oscillations in their ratio. This suggests a different role for new hadronic states.

We present a study of the decay J/ψ→γη${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ using the Mark III detector at the SLAC ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ storage ring SPEAR. A partial-wave amplitude analysis is performed on the η${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ system in the mass region from 1.2 to 1.5 GeV. We observe two η${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ resonances, each decaying via ${\mathit{a}}_0$(980)π. We identify one as the axial-vector meson ${\mathit{f}}_1$(1285) and the other as a pseudoscalar resonance at 1.40 GeV.