We discuss the derivation of Fujikawa’s method of the critical dimensions of the following models: the bosonic and N=1 locally supersymmetric nonlinear sigma models, and the N=2 and N=4 spinning strings. We argue that in the N=1 models the group-invariant measure is supersymmetric and does not lead to an extra anomaly. Our results are consistent with conjectured non-Abelian bosonization formulas for gravitational path integrals only for k=1, where k is the central extension of the Kac-Moody algebra.

The light matter supermultiplets are specified uniquely in most superstring theories when compactified on Calabi-Yau manifolds. It is pointed out that the discrete symmetries considered earlier in these models cannot give rise to a phenomenologically consistent fermion mass spectrum and suppress fast proton decay. We propose here a simple model which demonstrates the type of discrete symmetries one has to look for to make the superstring theories phenomenologically acceptable. Some interesting consequences of the model are pointed out.

The Lüscher term found in the QCD string model and in Monte Carlo lattice gauge calculations is significantly modified by vacuum polarization due to light-quark loops. This modification improves agreement with experiment.

The β function of SU(3) lattice gauge theory with three flavors of light dynamical quarks is obtained numerically by use of the (improved) ratio method. It appears to have a dip structure similar to that found in the theory without quarks. Our data seem to suggest that deviations from asymptotic scaling may be small for β≳5.3.

We calculate by lattice numerical methods the spin-dependent potentials relevant for heavy-quark spectroscopy. We find a long-range nonperturbative component in one of the spin-orbit potentials, whereas all other potentials exhibit a short-ranged perturbative behavior.

If there exists a heavy isosinglet h quark that mixes with the d quark in the weak eigenstates, then the neutral meson $H^0$(hd¯) can mix maximally with its antiparticle H${¯}^0$(h¯d) through lowest-order flavor-changing neutral currents regardless of how small the h-d mixing angle may be. The $H^0$-H${¯}^0$ mixing parameter ε depends essentially on the $H^0$ mass; for $m_H$<25 GeV, ε can be as large as 0.4.

Quantum analogs of Kolmogorov-Arnol’d-Moser tori and chaos in a periodically pulsed single-spin system are studied in the semiclassical regime. Wave functions (quasienergy states) are described in a spin-coherent state representation. Their projected binary-phase patterns are characterized in terms of the fractal dimensions of their perimeters.

By observing the reaction γγ→$K_s^0$$K^{\pm }$${\pi }^{\mp }$, the TPC/Two-Gamma experiment at the SLAC $e^{+}$$e^{\mathrm{-}}$ storage ring PEP has obtained a 95%-confidence-level limit of ${\Gamma }_{\iota \to \gamma \gamma }$B(ι→KK¯π)<1.6 keV for the ι(1450) meson. If, as is likely, the ι decays predominantly into KK¯π, the resulting ${\Gamma }_{\iota \to \gamma \gamma }$ limit appears to conflict with previous assignments of an observed ργ decay to ι and also with many analyses of η-η’-ι mixing. The contrast of this small γγ width with the large rate for J/ψ→γι is evidence that the ι is a glueball with little admixture of qq¯ states.

We suggest that electron and positron peaks seen in large-Z heavy-ion collisions originate in the decay of nontopological solitons consisting of a quasielectron and quasipositron which are formed in a new vacuum phase.

Data for the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(${\pi }^{+}$,2p) reaction at Tπ=160 MeV were obtained for a number of angle pairs. The resultant angular correlations for $T_1$+$T_2$>160 MeV (guaranteed pion absorption) peak at a separation angle corresponding to absorption on a deuteron at rest. However, simple estimates of initial- and final-state scatterings suggest that less than 50% of the absorption cross section arises from absorption on nucleon pairs. The data show little evidence for scattering of pions before absorption on nucleon pairs.

Levels in ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$ have been established up to 38ħ in the yrast band and about 30ħ in two sidebands. Below spin 20, the similarity to the isotone ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ is striking, but up to spin 34 ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$ remains rather collective while ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ becomes triaxial and evolves toward an oblate shape. This appears to result from small shifts in particle-alignment (backbend) frequencies; a proton alignment occurs before neutron ones in ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$, whereas the reverse is true in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$.

Two electronic equilibrium configurations for two-electron atoms have been derived exactly from the classical equations of motion. In these configurations the atom rotates as a whole like a rigid body. No further equilibrium is shown to exist. Semiclassical quantization of the rotation predicts two series of resonances converging to the double ionization threshold. This atomic-rotation spectrum is substantially different from its molecular and nuclear analog due to long-range Coulomb interactions.

Sympathetic cooling of trapped ions has been demonstrated in an experiment where ${}_{}{}^{198}{}_{}{}^{}\mathrm{Hg}_{}^{+}{}_{}{}^{}$ ions were confined in a Penning ion trap with laser-cooled ${}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{+}{}_{}{}^{}$ ions. ${}_{}{}^{198}{}_{}{}^{}\mathrm{Hg}_{}^{+}{}_{}{}^{}$ temperatures below 1 K were achieved. Ion plasma sizes, shapes, and rotation frequencies were measured. Dramatic changes in the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{+}{}_{}{}^{}$ plasma were observed when the ${}_{}{}^{198}{}_{}{}^{}\mathrm{Hg}_{}^{+}{}_{}{}^{}$ ions were introduced into the trap. These observations are consistent with the prediction of centrifugal separation for ions of different charge-to-mass ratios.

Production of LMM-Auger and ${\mathrm{L}}_1$${\mathrm{L}}_{23}$M-Coster-Kronig electrons in 60-keV ${\mathrm{O}}^{6+}$+He and 40-keV ${\mathrm{C}}^{4+}$+He collisions were measured with high resolution by the method of 0° Auger spectroscopy. Oxygen impact is found to create intense Coster-Kronig lines attributed to the configurations 1${\mathrm{s}}^2$2pnl with n≥6 which are produced by double-electron capture. Strong evidence is provided that the double-capture process involves electron-correlation effects whose analysis leads beyond the independent-electron model.

A semiclassical approach is used to derive, and extend to first order in g-2, the equilibrium degree of polarization in high-energy electron storage rings (the Derbenev-Kondratenko formula). Statistical concepts are shown to be essential for an understanding of this phenomenon. In so doing, some aspects of the polarization mechanism not previously recognized are uncovered.

We report direct measurements of vortex diffusivity, D, as a function of temperature through the Kosterlitz-Thouless transition. We find that D is a rapidly varying function of temperature near the transition. It is very small well below the transition, increases to ∼ħ/m at the static transition temperature, and apparently diverges at the point where the superfluid density vanishes. The diffusivity appears to be insensitive to the presence of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ impurities and to the nature of the substrate.

The Miesowicz viscosities ${\mathrm{\eta }}_1$, ${\mathrm{\eta }}_2$, and ${\mathrm{\eta }}_3$ and the Leslie coefficients ${\gamma }_1$ and ${\gamma }_2$ of perfectly aligned nematics are determined by nonequilibrium molecular-dynamics simulations. The results are compared with theoretical predictions and with experimental data.

An algebraic treatment of continuous spectra based on noncompact groups is extended to allow discussion of dissociation from bound states. Transition matrix elements between bound and continuum states can be evaluated algebraically by the construction of transition operators that transform according to the infinite-dimensional unitary representations of the noncompact dynamical group. The method is employed to calculate dissociation rates in the Morse potential, for which the relevant group is SO(2,1).

Stochastic cellular automata (SCA) with fixed, but randomly chosen, probabilities (spatial disorder) are studied in D dimensions. For zero disorder, the present SCA reduce to directed percolation in (D+1) space-time, but finite spatial disorder is incompatible with the critical exponents of directed percolation. Monte Carlo calculations of the SCA on several disordered structures in D=1 and D=2 yield new universal exponents. I also discuss the phase diagram of ‘‘diluted’’ SCA, which contains a multicritical point and the SCA analog of a ‘‘Griffiths phase’’ with nonexponential relaxation.

We report x-ray reflectivity measurements on the free surface of dodecylcyanobiphenyl (12CB) at the isotropic to smectic-A phase transition. At about 10?deC above ${\mathrm{T}}_{\mathrm{IA}}$, smectic-A-like ordering develops at the surface while the bulk phase remains isotropic. The angular dependence of the specular reflectivity is consistent with a sinusoidal density modulation, starting at the surface and terminating abruptly, after an integral number of bilayers. As the transition is approached the number of layers increases in quantized steps from zero to five before the bulk undergoes a first-order transition to the smectic-A phase.