The spin Berry phase can be observed in conductance experiments on rings of noncentrosymmetric materials. It results in destructive interference and in the shift of the Aharonov-Bohm oscillations. The spin-orbit interaction in vacuumlike Aharonov-Bohm experiments leads to the opposite sign of the magnetoresistance in comparison with the weak localization regime in disordered conductors. A time-dependent uniaxial strain results in current in a ring.

We find a drastic difference between the magnetoresistance of normal-metal (Ag) mesoscopic rings with superconducting boundaries (mirrors) and that of plain rings. The amplitude of h/2e Aharanov-Bohm oscillations is enhanced more than 100 times in rings with mirrors in the measuring leads. Rings with mirrors in stubs perpendicular to the current flow show h/4e and h/2e oscillations and evidence of a superconducting transition. The resutls are interpreted as due to a phase coupling between the superconductors via normal electrons, and to a confinement of quasiparticles to the ring by Andreev reflections.

We have performed density-functional-theory (DFT) calculations for potassium adsorbed on GaAs(110). The results show that alkali adatoms mainly act as donors giving their electrons to Ga-derived surface states. We found that these states consist of well localized Ga dangling bonds, which allowed us to map the DFT results on a two-dimensional Hubbard model. To calculate the Hubbard U and the charge-transfer parameter Δ we simulate the electron transfer between adjacent orbitals. We find that U and Δ are of the same order as the hopping integral t, which brings the surface in the Mott-Hubbard regime.

We study topological order and edge excitations of the ν=1/2 fractional quantum Hall state (FQH) of spin polarized electrons in a single-layer system. We find that the 1/2 FQH state obtained in the numerical study of Greiter et al. has a non-Abelian topological order suggested by Moore and Read. The edge excitations in such a non-Abelian FQH state are found to be described by the U(1) Kac-Moody algebra plus a chiral Majorana fermion theory. The electron and the quasiparticle propagators are calculated. Some experimental consequences are also discussed.

The resonant forward scattering of x-rays from ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nuclei is strongly polarization dependent. The broad-band excitation provided by synchrotron radiation (SR) results in an interesting time-dependent polarization mixing, which we will discuss. Further we demonstrate that by selecting only the component of the transmitted radiation which has a 90° rotated plane of polarization, the nonresonant (nonrotated) transmitted intensity can be substantially reduced. This new technique will allow full utilization of new powerful SR sources currently under construction.

We propose a new method to estimate the quenched free energy in disordered systems. It uses generalized thermodynamic potentials, given by annealed averages of the partition function with appropriate constraints realized by the aid of Lagrange multipliers. The method is applied to Ising models with random magnetic fields. In that particular case, the constraints correspond to average only over the disorder configurations where the sum of the random variables has the correct mean value and variance.

Finite-size scaling allows the extraction of a dimension from scaling ${\mathit{d}}_{\mathit{s}}$, as well as critical exponents for systems with a second-order phase transition. The calculation of ${\mathit{d}}_{\mathit{s}}$ allows comparisons to be made with other expansions in dimension, in which ${\mathit{d}}_{\mathit{s}}$ plays the role of the physical dimension. This is demonstrated by a numerical transfer-matrix study of the pure ferromagnetic Ising model in two and three dimensions, as well as for quenched random bonds in the two-dimensional Ising ferromagnet.

We study gravitational radiation reaction in the equations of motion for binary systems to post-Newtonian order [O(v/c${)}^2$] beyond the quadrupole approximation. The method uses post-Newtonian expressions for energy and angular momentum flux to infinity, and an assujption of energy and angular momentum balance. The equations of motion are valid for general binary orbits. We discuss the coordinate-system dependence of the radiation-reaction formula.

An exact solution of Einstein’s vacuum field equations describing a spherical-fronted impulsive gravity wave is given in a coordinate system in which the metric tensor is continuous across the (future null cone) history of the wave front in Minkowskian space-time. A coordinate transformation is presented which reduces the line element to Minkowskian form in the future of the null cone (it is manifestly in Minkowskian form in the past of the null cone) and enables us to demonstrate how the solution has been constructed using the Penrose procedure of subdividing flat space-time into two halves with the future null cone as boundary and then reattaching the halves with a warp.

Much of the mass of the Universe is thought to reside in some as yet unidentified dark matter. This view is based on the analysis of trajectories of luminous ‘‘tracers’’ that map out the local potential, assuming that gravity is the only long ranged interaction between ordinary and dark matter. This assumption should be tested experimentally if possible. Laboratory tests of the weak equivalence principle can constrain (at an interesting level) any exotic coupling between ordinary and dark matter when analyzed as a test of the uniformity of free fall towards the center of the Galaxy.

We tested the equivalence principle (EP) for Be, Cu, and Al falling toward the galactic center, and found Δa(Be,Cu)=-(0.1 ±5.8)×${10}^{\mathrm{-}12}$ cm/${\mathit{s}}^2$ and Δa(Be,Al)=(3.6±6.9)×${10}^{\mathrm{-}12}$ cm/${\mathit{s}}^2$. As dark matter is thought to account for (25–30)% of our galacticentric acceleration, the EP parameters for Be/Cu, or Be/Al, falling toward dark matter, are η(Be,Cu)=(0.0±1.2)×${10}^{\mathrm{-}3}$ and η(Be,Al)=(0.7±1.4)×${10}^{\mathrm{-}3}$ (1σ errors). This limits any EP-violating component of our acceleration toward dark matter and provides laboratory evidence that gravitation is the only significant long-range interaction between dark and ordinary matter.

Observations of the Small Magellanic Cloud using the Energetic Gamma Ray Experiment Telescope on the Compton Observatory yield an upper limit (95% confidence) for gamma-ray emission >100 MeV of 0.5×${10}^{\mathrm{-}7}$ photon/${\mathrm{cm}}^2$ s. The expected flux if the cosmic rays are universal rather than galactic in origin, is (2.4-0.5)×${10}^{\mathrm{-}7}$ photon/${\mathrm{cm}}^2$ s, only a third of which arise from cosmic ray electron interactions. Hence, the bulk of the cosmic ray energy density is almost certainly not metagalactic, and therefore galactic in origin.

Superstrings have been postulated based on parafermionic partition functions which permit spacetime supersymmetry by generalized Jacobi identities. A comprehensive search finds new such identities. Quadrilateral anomaly cancellation gives constraints on allowed chiral fermions. Bosonic left movers and ${\mathit{Z}}_4$ parafermionic right movers combine in a new heterotic superstring, more constrained than the old one, yet equally applicable to physics.

A high-statistics study by the Columbia-Chicago-Fermilab-Rochester Collaboration of opposite-sign dimuon events induced by neutrino-nucleon scattering at the Fermilab Tevatron is presented. A sample of 5044 ${\nu }_{\mathrm{\mu }}$ and 1062 ν${\mathrm{¯}}_{\mathrm{\mu }}$ induced ${\mathrm{\mu }}^{\mp }$${\mathrm{\mu }}^{\pm }$ events with ${\mathit{P}}_{\mathrm{\mu }1}$≥9 GeV/c, ${\mathit{P}}_{\mathrm{\mu }2}$≥5 GeV/c, 30≤${\mathit{E}}_{\nu }$≤600 GeV, and 〈${\mathit{Q}}^2$〉=22.2 ${\mathrm{GeV}}^2$/${\mathit{c}}^2$ is observed. The data support the slow-rescaling model of charm production with a value of ${\mathit{m}}_{\mathit{c}}$=1.31±0.24 ${\mathrm{GeV}}^2$/${\mathit{c}}^2$. The first measurement of the ${\mathit{Q}}^2$ dependence of the nucleon strange quark distribution xs(x) is presented. The data yield the Cabibbo-Kobayashi-Maskawa matrix element ‖${\mathit{V}}_{\mathit{c}\mathit{d}}$‖=0.209±0.012 and the nucleon fractional strangeness content ${\mathrm{\eta }}_{\mathit{s}}$=0.${064}_{\mathrm{-}0.007}^{+0.008\mathrm{}}$.

A search for the lepton mumber violating decay of the τ lepton to the γμ final state has been performed with the CLEO II detector at the Cornell ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ storage ring CESR. In a data sample that corresponds to an integrated luminosity of 1.55 ${\mathrm{fb}}^{\mathrm{-}1}$, we observe no candidates in the signal region. We thus determine an upper limit of B(${\mathrm{\tau }}^{\mathrm{-}}$→γ${\mathrm{\mu }}^{\mathrm{-}}$)<4.2×${10}^{\mathrm{-}6}$ at 90% confidence level.

We describe some implications for massive dihadron production experiments of recent observations in Fermilab experiments E609 and E557 of large nuclear rescattering effects in dijet production in hard pA collisions. Substantial upward corrections to α (in the ${\mathit{A}}^{\mathrm{\alpha }}$ cross section parametrization) are indicated for dihadron experiments which detect symmetric back-to-back hadrons with narrow acceptance in azimuth or ${\mathit{p}}_{\mathit{T}}$. Other consequences of the large nuclear rescattering are also discussed.

The (${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{\mathrm{-}}$) double-charge-exchange reaction for pion energies of 200 to 1400 MeV is calculated with a zero-parameter Glauber theory that includes spin flip and pion absorption. Differential cross sections and excitation functions are obtained for ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ targets. Results for ${\mathit{T}}_{\mathrm{\pi }}$=300–525 MeV are compared with recent experimental results and suggest a new quenching process. We have calculated effects of medium polarization on the isovector pion operator and find a strong reduction in good agreement with data. A pronounced dip in the cross section near ${\mathit{T}}_{\mathrm{\pi }}$=1300 MeV offers a unique testing ground for unconventional mechanisms.

In a plunger experiment the mean life of the (ν${\mathit{f}}_6^2$×$3^{\mathrm{-}}$×$3^{\mathrm{-}}$)${12}^{+}$ state at 3.981 MeV in ${}_{64}{}^{148}{}_{}{}^{}\mathrm{Gd}_{84}^{}{}_{}{}^{}$ was measured at τ=83(10) ps, giving 77(11)${\mathit{B}}_{\mathit{W}}$ for the 1286 keV ${12}^{+}$→$9^{\mathrm{-}}$ E3 transition rate, confirming the double-octupole character of the ${12}^{+}$ state. The observed deviations in energy and transition rate from harmonic vibration are shown to be caused by the exclusion principle acting between nucleons in the two phonons and are related to the dominant contributions to the ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$ octupole phonon of the low-lying Δl=Δj=3 proton and neutron in-shell $3^{\mathrm{-}}$ excitations which are of vital significance for the octupole mode in open-shell nuclei.

The electronic structure of hydrogen and muonium at the bond-centered site in diamond is investigated using ab initio cluster calculations. Based on a Hartree-Fock calculation, correlation effects are accounted for by a configuration interaction expansion. The hyperfine and superhyperfine parameters for anomalous muonium are determined by averaging over the spread of the muon wave function. Good agreement with experimental hyperfine parameters is found and values for the superhyperfine interaction, which can be detected in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ enriched samples, are predicted.

The nuclear size correction to the self-energy of an electron in the 1${\mathit{S}}_{1/2}$, 2${\mathit{S}}_{1/2}$, or 2${\mathit{P}}_{1/2}$ state in hydrogenlike ions is calculated. The results modify theoretical predictions required for experimental tests of quantum electrodynamics in strong fields, and they resolve differences among previous calculations for the Lamb shift in hydrogenlike uranium. Results are presented for a number of elements ranging from iron (Z=26) to fermium (Z=100). An estimate of the nuclear model dependence of the effect is made, and, based on the numerical results, a simple formula for the correction as a function of the nuclear radius is provided.