We report observation of circular dichroism in reflection from various cuprate superconducting materials, including ${\mathrm{YBa}}_2$${\mathrm{Cu}}_2$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ films, an etched ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ crystal, and a ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ crystal. This signal develops as T is lowered below 200 K and exhibits little change near ${\mathit{T}}_{\mathit{c}}$. The exact onset temperatures differ for the various materials.

We report the experimental observation of a sustained standing nonequilibrium chemical pattern in a single-phase open reactor. Considering the properties of the pattern (symmetry breaking, intrinsic wavelength), it is interpreted as the first unambiguous experimental evidence of a Turing structure.

Learning and generalization by a perceptron are described within a statistical-mechanical framework. In the specific case considered here, the goal of learning is to infer the properties of a reference perceptron from examples. As the number of examples is increased a transition to optimal learning at finite temperature is found: The generalization error can be decreased by adding thermal noise to the synaptic coupling parameters. Although the transition is weak, significant improvement can be achieved further beyond the threshold.

The relativistic generalization of the quantum-mechanical virial theorem is derived and used to clarify the connection between the nonrelativistic and (semi)relativistic treatment of bound states.

The metric perturbation produced by a collapsing ‘‘knot’’ of global texture in a flat background is calculated. This is used to calculate the energy shift for photons traversing such knots, leading to a prediction for the microwave anisotropy pattern produced in the global-texture scenario for large-scale structure formation. The metric is also used to calculate the velocity field induced in nonrelativistic matter, on scales well inside the horizon. This would produce an early generation of small gravitationally bound objects. At larger scales, the texture field would induce coherent velocity fields on a scale comparable to that seen in galaxy surveys.

We present a dynamical mechanism for completing inflationary phase transitions via bubble nucleation which can satisfy all known constraints for a wide spectrum of models and parameters. The approach is a generalization of the recent ‘‘extended inflation’’ model which corrects a serious flaw. We find an essentially model-independent bubble-size distribution which may be important for large-scale structure.

The widely used Tremaine-Gunn phase-space constraint giving lower-mass limits for neutrino dark matter is extended to bosons. The occupation number for a boson gas does not in general have a maximum, but only a small fraction primordial bosons in equilibrium have large occupation numbers. Dark galaxy halos formed dissipationlessly from primordial bosons therefore have fairly low coarse-grained phase-space number densities. This leads to mass lower limits in the eV range for bosonic dark-matter candidates, only slightly smaller than for fermions.

A realization of the ‘‘flavor-democracy’’ approach to quark and lepton masses is provided in the context of the standard model with a horizontal ${\mathit{S}}_3$ permutation symmetry. In this model, t and b quarks pick up mass at the tree level, c, s-quark and τ-lepton masses arise at the one-loop level, u, d, and μ masses at the two-loop level, and the electron mass at the three-loop level, thus reproducing the observed hierarchial structure without fine tuning of the Yukawa couplings. The pattern of quark mixing angles also emerges naturally, with ${\mathit{V}}_{\mathit{u}\mathit{s}}$,${\mathit{V}}_{\mathit{c}\mathit{b}}$≊O(ε), ${\mathit{V}}_{\mathit{u}\mathit{b}}$≊O(${\mathrm{\epsilon }}^2$), where ε is a loop expansion parameter.

Contributions to neutrino scattering which are proportional to 1/${\mathit{Q}}^2$ are estimated using vector and axial-vector meson dominance. They are found to be potentially larger than previous estimates of nonleading twist. They lead to an additional theoretical uncertainty, on the order of ${}_{\mathrm{-}0.00}{}^{+0.01\mathrm{}}{}_{}{}^{}$, in the value of ${\sin }^2$${\mathrm{\theta }}_{\mathit{W}}$ which is extracted from the neutrino cross-section ratio ${\mathrm{\sigma }}^{\mathrm{NC}}$/${\mathrm{\sigma }}^{\mathrm{CC}}$. This suggests that the mass of the top quark is likely to lie near the lower end of its currently allowed range in the minimal standard model.

We report on results of a dedicated search for the CP-violating decay ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^0$${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$. We have found no evidence for this decay mode and obtain a 90%-confidence upper limit of 5.5×${10}^{\mathrm{-}9}$ for its branching ratio.

The first kinematically complete, good-statistics data for the (π,2π) reaction on the proton are presented. They involve double- and triple-differential cross sections as well as ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ angular correlations. At energies around the Δ resonance, they exhibit a marked difference from phase space. The data are qualitatively described within the framework of an extension of Weinberg’s effective chiral Lagrangian.

We report the observation of eight unexpected energy levels close to but clearly different from ${\mathrm{H}}_2$ ${\mathit{B}}^1$${\mathrm{\Sigma }}_{\mathit{u}}^{+}$ levels. In transitions involving these levels vacuum-ultraviolet transitions terminating in p-${\mathrm{H}}_2$ levels are observed subsequent to two-photon Q(1) excitation ${\mathit{X}}^1$${\mathrm{\Sigma }}_{\mathit{g}}^{+}$(v’’=0)→EF ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathit{g}}^{+}{}_{}{}^{}$(v’=6) of o-${\mathrm{H}}_2$. Several findings indicate that these strange levels may be a manifestation of electronically excited ${\mathrm{H}}_4$, which has been discussed in a number of theoretical contributions.

We determined electron binding energies from multiply charged Kr ions from internal-conversion-electron spectra for the 9.4-keV transition in ${}_{}{}^{83}{}_{}{}^{}\mathrm{Kr}_{}^{\mathit{m}}{}_{}{}^{}$. Because our radioactive source is a low-density gas, we can observe the electrons from ionic states produced by the vacancy cascade of the preceding highly converted transition. We report binding-energy shifts for the 2s, 3s, and 4s orbitals in the configuration of the atomic ground state. For charge state $7^{+}$, i.e., for Ni-like Kr and higher, we also observe the shifts from metastable states.

It is found that strong squeezing can be obtained by special superposition of coherent states along a straight line in the α -plane. This mechanism opens new possibilities for squeezing, e.g., of the molecular vibrations during a Franck-Condon transition induced by a short coherent light pulse.

We report experimental evidence that, beyond the transition for spatiotemporal chaos, Rayleigh-Bénard convection displays thermodynamic properties in Fourier space. It is shown that a generalized temperature may be defined using the natural fluctuations of the system, and that a suitable free energy accounts for the experimental results.

We overcame the strong Gγ=-3+${\nu }_{\mathit{y}}$ intrinsic depolarizing resonance using a Siberian snake acting on a stored beam of 177-MeV polarized protons at the Indiana University Cooler Ring. We also saw the first evidence for a synchrotron depolarizing resonance in a proton ring. Two synchrotron resonances were studied by varying the rf accelerating voltage and the imperfection field at 104 MeV. The Siberian snake also overcame these synchrotron depolarizing resonances.

We describe the first investigation of the nonclassical radiation field of a micromaser. The maser cavity is cooled to 0.5 K to exclude thermal photons and has a quality factor 3×${10}^{10}$. Velocity-selected Rydberg atoms pump the maser. The photon statistics in the cavity are measured via the statistics of the atoms leaving the cavity in the lower maser level. Taking into account a detection efficiency of 10%, their fluctuations are reduced up to 40% below the Poisson level. This corresponds to photon-number fluctuations in the cavity of up to 70% below the vacuum-state limit.

We have measured the correlation in frequency-dependent intensity fluctuations in the total transmission through random dielectric samples, using visible light in a (essentially) plane-wave geometry. The correlation function, of which the width at half maximum is proportional to ${\mathit{L}}^{\mathrm{-}2}$ (L is the thickness of the sample), decays as (Δω${)}^{\mathrm{-}1/2}$. This constitutes the experimental proof for the buildup of long-range intensity correlations in the propagation of classical waves by multiple scattering.

The statistics of a self-avoiding walk of N steps on a lattice in a field of asymmetric obstacles is developed. The obstacles are modeled by rigid rods of asymmetry ratio r oriented preferentially and/or by stretched flexible molecules. Each obstacle consists of N segments, each one of which occupies one lattice site. The size, shape, and entropy of the molecule represented by the self-avoiding walk are obtained. The scaling law deviates from the conventional no-obstacles limit (ν=0.6) only for large concentrations of obstacles. However, the molecule is elongated even for a small concentration of obstacles. Because the formulas are so easily obtained and extended the method promises to be widely applicable.

We have observed the ballistic-phonon-focusing pattern along the [100] axis of a 1-mm-thick silicon crystal using α-particle bombardment as the phonon source. These experiments on phonon-mediated particle detection are performed in vacuum at about 400 mK and use titanium-superconducting-transition-edge phonon sensors on the crystal surfaces. The ballistic time of flight is confirmed in one experiment and the focusing patterns are spatially resolved in another. These data indicate that about 1/3 of the phonon energy striking the back face during the first μsec is ballistic.