A full-torus, compressible, resistive MHD simulation reveals that in the slow ramp phase of tokamak sawtooth oscillations an ideal kink mode slowly emerges at the magnetic axis as a result of current peaking and gradually expands radially outwards, forming a crescent-shaped poloidal magnetic structure that allows the central q value to go substantially below 1. Its converging return flows drive nonlinear reconnection to make two magnetic islands. The kink mode turns into a resistive convection type with a slow but larger growth rate. As the flow grows substantially, a large-scale rigid flow arises and suddenly crashes the plasma structure, forming a crescent-shaped pressure distribution.

Multipair excitations in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ at low temperature are investigated using a sum-rule approach. The ${\mathit{m}}_3$=FS(q,ω)${\mathrm{\omega }}^3$ dω sum rule is calculated microscopically by properly accounting for short-range correlations. The average spin multipair (mp) energy ${\mathrm{\omega }}_{31}^{\mathit{i}}$[${\mathit{m}}_3^{\mathit{i}}$(mp)/${\mathit{m}}_1^{\mathit{i}}$(mp)${]}^{1/2}$ is found to be ∼50 K in the low-q limit. A rigorous lower bound for the multipair contribution to the static form factor in the low-q limit is derived. The relative importance of coherent and spin-dependent multipair excitations is also discussed.

Synchrotron x-ray diffraction studies using a diamond-anvil cell and an imaging plate reveal that solid bromine begins to undergo a molecular-to-monatomic phase transition near 80 GPa. The structure of the high-pressure phase is found to be body-centered orthorhombic ($D_{2h}^{25}$-Immm), as previously observed in iodine above 21 GPa. These results on bromine plus the previous data on iodine and iodine monobromide show that the molecular dissociation takes place when the scaled unit-cell volume as ṽ=v/8$r_s^3$ in the molecular phase ($r_s$ is the intramolecular bond length in the solid) reaches v${̃}_c$=1.29. We also observe universal behavior of the scaled lattice constants versus ṽ in all solid halogens.

A high-sensitivity ac calorimeter system has been developed to investigate the temperature variation of the heat capacity from free-standing liquid-crystal films. We have observed a clear evolution of the heat-capacity anomaly from films of the liquid-crystal compound 650 BC as the films are reduced in thickness from 10 to 4 molecular layers near their bulk smectic-A–hexatic-B transition. Here 650BC refers to n-hexyl-4’-n-pentyloxybiphenyl-4-carboxylate. The four-layer films show a single, sharp, and cusplike heat-capacity peak without thermal hysteresis.

The total dynamics structure factor S(k,ω) measured by neutron scattering on a mixture of 80% He and 20% Ne at 39.3 K and total number density 15.1 ${\mathrm{nm}}^{\mathrm{-}3}$ shows clear side peaks or shoulders at frequencies ω=${\mathrm{\omega }}_{\mathrm{s}}^{\mathrm{}\left(1\right)\mathrm{}}$(k) for wave numbers k up to ≊15 ${\mathrm{nm}}^{\mathrm{-}1}$. $omega sub s sup (1) (k)>ck— (with c the velocity of sound) in agreement with the predicted existence of a fast sound mode in mixtures, due to oscillations in the light component (1) alone.

Employing Monte Carlo techniques, the diffusion and drift of charge carriers within an array of hopping states subject to a Gaussian distribution of site energies of width σ has been studied as a function of σ/kT and electric field. With increasing disorder and field, significant deviations from Einstein’s law are noted. They are shown to be the consequence of anomalous, field-assisted diffusion while the mobility remains constant. The effect can account for anomalous transit-time dispersion observed in polymeric photoconductors exhibiting time independent transport.

The nature of non-self averaging behavior in the kinetics of domain growth is studied by Monte Carlo simulations. Fluctuations in the scaling regime of the two-dimensional spin-flip Ising model are found to involve multiscaling, as is known from other problems, such as percolating resistor networks and diffusion-limited aggregation. The frequency-dependent fluctuations in the scaling regime are found to be 1/f-like: The power spectrum obeys 1/${\omega }^{\phi }$, where ω=2πf is the frequency and φ≊0.9. These results can be tested experimentally.

Anomalous photoinduced current transients in the nematic phase are experimentally observed by illuminating a liquid-crystal sample with a xenon-flash-lamp pulse while applying a dc voltage. The response time is fast, of the order of a microsecond, and independent of the magnitude of the applied voltage. The peak current is independent of the wavelength of the light and displays a critical response near the nematic-isotropic phase-transition temperature. Pyroelectricity in nematic liquid crystals is proposed as the physical origin of the phenomenon.

We show that low-energy, helium ion scattering in the forward direction provides a surface specific means for directly observing adsorbed deuterium. Energy spectra of 1-keV ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ scattered at angles less than 30° from a surface with adsorbed D contain the two maxima predicted for classical single scattering. Angular studies indicate that D atoms adsorbed on the Pd(110) surface at room temperature reside in the troughs between atom rows.

The neutral sputtered flux from a Ru single crystal oriented along the (0001) axis has been determined as a function of primary ion dose in real time using nonresonant photoionization techniques coupled with time-of-flight mass spectrometry. The data reveal, surprisingly, that the sputtering yield is twice as large from an undamaged surface as that from a slightly damaged surface. The sputtering yield decreases until steady state is reached at a primary ion fluence of only 2×${10}^{15}$ ions ${\mathrm{cm}}^{\mathrm{-}2}$. Data analysis results in an estimated cross section for damage of (2.7±1.0)×${10}^{\mathrm{-}15}$ ${\mathrm{cm}}^2$.

Magnetic moments per atom in the thermodynamically stable pseudomorphic monolayer Fe(110) on W(110), coated with Ag, were determined by magnetometry in UHV above 220 K. Extrapolation to T=0 using temperature-dependent magnetic hyperfine fields, measured by conversion electron Mössbauer spectroscopy, results in ground-state moments enhanced by (14±5)% in comparison with bulk Fe.

A magnetic state of orbital nature is predicted in deformed metal clusters. The restoring force of this state originates from a quantum effect associated with the kinetic Fermi motion. For Na clusters the frequency is predicted to be ${\omega }_{M1}$=δ4.6$N^{\mathrm{-}1/3}$ eV where δ is the deformation of the cluster.

We present existing theory on two-dimensional transitions (appropriate to thin parallel-plate geometries) in such a way that one can identify easily conditions for the onset of shallow cells. By doing so we can give conditions under which succinonitrile-acetone mixtures should undergo supercritical bifurcation in experimentally accessible ranges. These results suggest a means for the quantitative test of the Mullins and Sekerka model and its weakly nonlinear extensions.

We present an approximate solution of the Einstein equations for the metric outside a monopole resulting from the breaking of a global O(3) symmetry. The monopole exerts practically no gravitational force on nonrelativistic matter, but the space around it has a deficit solid angle, and all light rays are deflected by the same angle, independent of the impact parameter.

We discuss the central charge in continuous families of two-dimensional conformal field theories. In a nonunitary conformal field theory the c theorem does not hold: A critical line can have a continuously varying central charge. This is illustrated with the bosonic-string ghost system and may pose difficulties for attempts to formulate string theory on the space of 2D field theories.

The internal space-time symmetry of rapidly moving composite particles is studied in terms of the little groups of the Poincaré group. It is shown that Feynman’s x in his parton picture is a gauge-transformation parameter.

The CDF (Collider Detector Facility) collaboration has recently announced limits on the masses of squarks and gluinos assuming that they decay directly to a massless lightest supersymmetric particle (LSP). We examine how these mass limits change when realistic squark and gluino decays to all gauginos are incorporated and the LSP mass is given by the minimal supergravity model. The gluino mass is diminished by 3–30 GeV as we vary the model parameters over their complete range. The squark mass limit is typically reduced by ≲10 GeV if m(LSP)≲20 GeV.

The ratio of sea to valence quarks for nucleons in tungsten has been measured for the fractional momentum range 0.04<$x_N$<0.36. The determination is based on the relative production rate of muon pairs by ${\pi }^{+}$ and ${\pi }^{\mathrm{-}}$ beams on a tungsten target. The results provide the most accurate determination to date of this ratio in the region $x_N$<0.1 and $Q^2$>20 ${\mathrm{GeV}}^2$, and are in good agreement with earlier measurements.

The first observation of superdeformation in the mass region A≃190 is reported. A rotational band of twelve transitions with an average energy spacing of 37 keV, an average moment of inertia ${\mathrm{scrF}}^{\mathrm{}\left(2\right)\mathrm{}}$ of 110 ${ħ}^2$ ${\mathrm{MeV}}^{\mathrm{-}1}$, and an average quadrupole moment of 18±3 e b has been observed in ${}_{}{}^{191}{}_{}{}^{}\mathrm{Hg}$; this band persists at low rotational frequency. These results are in excellent agreement with a calculation that predicts an ellipsoidal axis ratio of 1.65:1 for the superdeformed shape in this nucleus.

New experimental results are presented for short-pulse microwave ionization of highly excited hydrogen atoms. A comparison of these results with quantum numerical computations and analytical predictions provides for the first time experimentally grounded evidence of the localization phenomenon that leads to the suppression of the quantum version of the chaotic diffusion in action space occurring in the classical limit.