The detailed dependence of the smallest nonzero eigenvalue of a bistable periodic Fokker-Planck equation on the external-noise correlation time is determined for the first time numerically to tie down contrasting theoretical predictions. The isospectrality with the Fokker-Planck equation for the metastable system defined by inversion of the bistable potential is proved analytically. This amounts to a generalized supersymmetric transformation between the corresponding non-Hermitean Hamiltonian operators.

We have conducted an experiment to detect a composition-dependent force with range λ between 10 m and 1 km, and find a statistically significant effect. If interpreted as arising from a new force, this result and other recent measurementes would be consistent in strength only if the coupling were predominantly to nuclear isospin.

Under the assumption that charge conservation and charge quan- tization are exact, it is pointed out that the expectation values f the charges can still deviate from the exact quantized eigenvalues, as long as the charge superselection rule is not absolute. The deviations can be suppressed by a large energy scale, identified as the mass of the magnetic monopole. Existing experimental results are consistent with Δ$Q_p$+Δ$Q_e$≊3×${10}^{\mathrm{-}20}$e and Δ$Q_n$≊-3×${10}^{\mathrm{-}20}$e, where Δ$Q_i$ is the deviation for particle i. Implications, in particular &≊6×${10}^{\mathrm{-}20}$e, are discussed.

Four categories are defined of exotic and nonexotic first-class and second-class weak currents, three of which are suppressed in the standard model. Hadronic final states produced through various symmetry-breaking mechanisms are subject to selection rules which govern their allowed values of ${\mathrm{J}}^{\mathrm{PG}}$. We show that there are four types of suppressed transitions and give examples of each.

Results are presented on a search for neutral heavy leptons that couple to muon neutrinos in high-energy neutrino-nucleon interactions ($E_{\nu }$=30–230 GeV). No evidence for such particles is observed. We obtain upper limits on the coupling of neutral neavy leptons to ${\nu }_{\mu }$ below Fermi strength in the mass range 0.25–14 GeV/$c^2$.

The isovector parts of the effective nucleon-nucleon interaction are studied by examination of the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(p,n) at intermediate energies near zero momentum transfer with use of recently developed G-matrix and free–t-matrix interactions. The spin-independent coupling ($V_{\tau }$) exhibits a strong energy and density dependence which, in the case of the G matrix based on the Bonn potential, significantly improves the agreement between calculated values of ‖$V_{\sigma \tau }$/$V_{\tau }$${\Vert }^2$ at q=0 and those recently extracted from the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(p,n).

Results of a multidimensional (${\beta }_2$, γ, ${\beta }_4$, ω, Z, and N) search for nuclear superdeformed configurations are presented. Calculations based on a realistic deformed average field give a relatively strong dependence of the ‘‘super’’ elongation on the particle number. This dependence is shown to be a cyclic function of the particle number. It originates from the pseudospin and pseudo-SU(3) symmetries which are obeyed approximately in a realistic average field.

High-energy γ-ray spectra have been measured in coincidence with products from the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ge}$ at 15 and 24 MeV/nucleon. The evolution of the giant dipole resonance (GDR) is studied as a function of excitation energy ($E^{\mathrm{*}}$). Up to $E^{\mathrm{*}}$≊300 MeV the measured GDR strength is consistent with full collectivity. At higher $E^{\mathrm{*}}$ a strong inhibition of the GDR γ decay is observed. At the highest transition energies, the spectra are consistent with bremsstrahlung emission associated with nucleon-nucleon collisions.

Because of the large systematic uncertainties of Mott scattering, alternative methods for more accurate absolute electron polarimetry are presently being discussed. One of them is the measurement of the circular polarization of impact radiation produced by polarized electrons. The present paper shows that the transition $3^3$P→$2^3$${\mathrm{S}}_1$ (388.9 nm) from the unresolved $3^3$${\mathrm{P}}_{\mathrm{J}}$ multiplet of helium is very appropriate for the absolute calibration of electron polarization. This can be utilized to increase the accuracy of polarization analysis with a Mott detector.

New coherent transient optical effects are reported for resonantly excited three-level cesium atoms. Complex modulation of free-induction decay was observed and is attributed to dressed-atom effects. Contrary to prior expectations, coherent transients monitored for upper and lower transitions were remarkably dissimilar and provide clear evidence for coherence transfer between the upper and lower optical transitions.

We compare the effects of finite thickness and absorption on the line shape of the coherent backscattering peak from a disordered medium. By termination of the coherent random walk of photons through confined goemetry and/or absorption, contributions of different time-reversed paths to the line shape of the backscattering peak have been determined. Using circularly polarized light, we find good agreement between the experimental and calculated line shape of the helicity-preserving channel whose coherent backscattering peak closely resembles that of a scalar field.

A simple model is presented for the energy-cascading process in the inertial range that fits remarkably well the entire spectrum of scaling exponents for the dissipation field in fully developed turbulence. The scheme is a special case of weighted curdling and its one-dimensional version is a simple generalized two-scale Cantor set with equal scales but unequal weights (with ratio∼(7/3). This set displays all the measured multifractal properties of one-dimensional sections of the dissipation field.

Since the start of TMX-U operations we have observed weak oscillations with a frequency approximately twice the ion-cyclotron frequency at the end-cell midplane. Recent results show that this instability is driven at the sloshing-ion outer turning point. We find that the sloshing-ion lifetime scales inversely with the instability amplitude. The sensitivity of this instability to the cold-ion density shows that this is a loss-cone instability. These results have important implications for mirror fusion experiments as well as solar and space plasmas.

Tokamak discharges using the expanded boundary divertor in the DIII-D device exhibit H-mode confinement. With neutral-beam power up to 6 MW, energy confinement remains comparable to the Ohmic value at a plasma current of 1 MA. Confinement is also independent of plasma density and toroidal field. Confinement increases with plasma current, but the exact functional dependence is, as yet, uncertain. These results show that the H mode can be achieved in a reactor-compatible open divertor configuration.

With use of laser-induced fluorescence in the Caltech Encore tokamak, anomalously fast (40×classical) ion heating has been observed and found to correlate with the presence of large-amplitude drift-Alfvén waves. Using numerical simulations we demonstrate that the heating is stochastic and occurs when ion displacement due to polarization drift becomes comparable to the perpendicular wavelength, i.e., when $k_{\perp }^2$φ̃/${\omega }_{\mathrm{ci}}$$B_0$≃1. Stochastic heating may also be the cause of the anomalously high ion temperatures observed in reverse-field pinches.

An ultimate linac structure is realized by an appropriate crystal lattice (superlattice) that serves as a ‘‘soft’’ irised waveguide for x rays. High-energy (∼40 keV) X rays are injected into the crystal at the Bragg angle to cause Bormann anomalous transmission, yielding slow-wave accelerating fields. Particles (e.g., muons) are channeled along the crystal axis.

A new type of toroidally localized kink instability, which we named the ‘‘slinky mode,’’ was observed in a reversed-field–pinch plasma in the OHTE (Ohmic heating toroidal experiment) device. It is found that the slinky mode is the result of the phase locking of several internal kink modes due to nonlinear coupling and is an effective way to approach the Taylor relaxed state.

We consider the anomalous electron and heat transport in a tokamak plasma. The electrons are described by the nonlinear drift-kinetic equation. We analyze transport through the averaged response function in the presence of drift-Alfvén wave turbulence. In contrast to recent findings by Terry, Diamond, and Hahm, we conclude that magnetic fluctuations lead to a substantial transport of both parallel and perpendicular energies. The latter, previously neglected, is found to be significant and of the order of the test-particle diffusion.

The adsorbate-induced reconstruction of the room-temperature Ni(110)-H surface has been resolved by scanning tunneling microscopy. The structure, known as ‘‘streaky’’ (1×2) from LEED observations, is found to be primarily a (5×2) Ni reconstruction with small domain size along the 〈001〉. Top-layer Ni atoms are paired long the 〈001〉 by a 0.5-Å lateral displacement to form tetramers and every fifth 〈001〉 row is missing. The barrier height, measured simultaneously with a constant-current topograph, is found to be higher along the 〈001〉 missing rows.

The surface stress tensor is calculated from first principles for several Si(111)1×1, 2×1, and 2×2 surfaces. Contrary to widely held expectations, only a weak compressive stress is found for the unreconstructed 1×1 surface. Reconstructions involving π-bonded chains or adatoms are predicted to be under substantial tensile stress. The results indicate that relief of surface stress is not the driving force for the 7×7 reconstruction. The stress is shown to be useful in prediction of the effect of externally applied strain, which can drive changes in the surface reconstruction pattern.