Submonolayer coverages of gold on tungsten (110) surfaces cause only a minor work-function increase. Heating such a surface produces a large reversible work-function decrease which depends on coverage and temperature and which can be attributed to a two-dimensional phase transition.

Energy-dispersive x-ray diffraction studies have been made on BaTe to 410 kbar. It undergoes a first-order phase transition from the sodium chloride structure to the cesium chloride structure at 48 kbar. $P\left(V\right)$ data were obtained over the entire range. Optical studies indicated by extrapolation that metallization will occur for $\frac{V}{V_0}\sim 0.65$ while resistivity studies show directly that band-overlap metallization occurs at $\frac{V}{V_0}=0.65\mathrm{}$ and $P=200\mathrm{}$ kbar. The resistivity of the semimetallic phase is 600 μΩ cm at 300 K; the resistivity of the semimetallic phase varies linearly with temperature between 200 and 300 K.

In hole space-charge layers on silicon we observe lifting of the quasispin degeneracy by the surface electric field in the absence of an external magnetic field. This lifting is detected in a splitting of intersubband resonance transitions and increases with increasing surface carrier density, reflecting an increase with quasimomentum. We have performed calculations of the subband excitation spectrum which confirm the experimentally observed quasispin splitting.

A new superconducting state induced by an external magnetic field has been observed in the pseudoternary Eu-Sn molybdenum chalcogenides for different Eu concentrations. This phenomenon is explained in terms of the Jaccarino-Peter compensation effect which accounts correctly for the shape of the $H_{c2\mathrm{}}-T$ phase diagram.

With picosecond spectroscopy and molecular beams it is shown that nonchaotic multilevel vibrational energy flow is present in large polyatomic molecules. This Letter reports on this novel observation and its probing of the fundamental process of energy redistribution in molecules.

The geomagnetic field near the equator is used to measure the abundance ratio of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$/${}_{}{}^4{}_{}{}^{}\mathrm{He}$ near 6 GeV/nucleon. This ratio is found to be 0.24±0.05, under the assumption that the helium rigidity spectrum has the form $\frac{\mathrm{dI}}{\mathrm{dR}}\sim R^{-2.65\mathrm{}}$. If all ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is of secondary origin this implies an interstellar mean escape path length of ≈ 15 g/${\mathrm{cm}}^2$, a value considerably larger than that determined from observations of heavier elements, but compatible with measurements of the helium isotopic ratio at lower energies.

Evidence is presented for oscillatory and chaotic behavior of the electrical conduction measured in barium sodium niobate single crystals at elevated temperatures. Analysis of the chaotic state verifies the existence of a strange attractor, whose dimension and entropy are determined. The observations indicate a Ruelle-Takens-Newhouse scenario.

Consideration is given to equations of the form $\frac{\partial n}{\partial t}=D{\nabla }^{2}n+Q\left(n\right)\mathrm{}$; the reaction-rate $Q\left(n\right)\mathrm{}$ is such that $\frac{d^{2}Q}{d{n}^2}<~0$ for all values of $n>~0$. A lower bound $n_{-}=n_{-}(\overrightarrow{\mathrm{x}},t)\equiv 〈\gamma 〉 (<~n)$ is obtained as the expectation value of the solution to the associated Brownian-motion equation $\frac{\partial \gamma }{\partial t}=-\overrightarrow{\mathrm{u}}\mathrm{}\left(t\right)\mathrm{}·\nabla \gamma +Q\left(\gamma \right)$, where $\gamma =\gamma (\overrightarrow{\mathrm{x}},t)$ is an auxiliary stochastic variable and the random velocity $\overrightarrow{\mathrm{u}}\mathrm{}\left(t\right)\mathrm{}$ is Gaussian. An upper bound $n_{+} (>~n)$ emerges as a concomitant of $n_{-}$, and an approximate analytical solution is shown to be given by $\tilde{n}\equiv \frac{1}{2}(n_{-}+n_{+})$ with the accuracy bound $|n-\tilde{n}|<~\frac{1}{2}(n_{+}-n_{-})$ expressed analytically.

Time development of cellular automata in $d$ dimensions is mapped onto equilibrium statistical mechanics of Ising models in $d+1\mathrm{}$ dimensions. Directed percolation is equivalent to a cellular automaton, and thus to an Ising model. For a particular case of directed percolation we find ${\nu }_{\parallel }=2\mathrm{}$, ${\nu }_{\perp }=1\mathrm{}$, ${\eta }_{\perp }=0\mathrm{}$.

We prove Birkhoff's theorem in conformal gravity: The most general spherically symmetric, electrovac solution is static, and hence absolutely stable against spherically symmetric perturbations. This result goes beyond the zero-energy theorem since it applies even when the solution is not asymptotically flat. On the basis of the known examples, we conjecture that any field theory lacking linearized spin-0 modes possesses a Birkhoff theorem.

We derive the effective Lagrangian which describes the interaction between a charged particle and a magnetic moment in the nonrelativistic limit. It is shown that neutral particles with a magnetic moment will exhibit the Aharonov-Bohm effect in certain circumstances. We suggest several types of experiments.

We construct the five-dimensional ($d=5\mathrm{}$) Yang-Mills-Einstein supergravity with noncompact gauge group SU(3,1). This model is a unified theory in the sense that there is a symmetry connecting each field to all the others, and it is the unique $d=5\mathrm{}$ Yang-Mills-Einstein supergravity theory with this property. We show that consistency of the quantum theory requires the dimensionless product ${\kappa }^{-1\mathrm{}}{g}^s$ of gravitational constant and gauge coupling constant to be quantized.

Evidence is found for corrections to the soft-pion $S$-wave nonleptonic hyperon-decay amplitudes from the observed deviation from the generalized Lee-Sugawara relation $2A\left({\Xi }_{-}^{-}\right)+A\left({\Lambda }_{-}^0\right)+{\left(\frac{3}{2}\right)}^{\frac{1}{2}}A\left({\Sigma }_{-}^{-}\right)=0\mathrm{}$. These corrections, assumed to come from the low-lying ${\mathrm{½}}^{-}$ excited baryon intermediate states, are estimated experimentally with use of the expressions suggested by the quark model and are found to reduce significantly the soft-pion results.

A simple theorem is proved about the $\bar{\theta }$ parameter in grand unified models with spontaneous $\mathrm{CP}$ symmetry breaking. This theorem states two conditions on such models which, if fulfilled, imply that $\bar{\theta }$ is zero at tree level. Models which fulfill these conditions are generalizations of a recent model of Nelson and are easy to construct.

A unified approach is used to describe quasielastic and fusion processes in heavy-ion reactions at near barrier energies. The spin distributions for fusion are used in conjunction with transition-state theory to calculate fission fragment angular distributions. Results for the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ show that when transfer contributions are small, satisfactory agreement with data is obtained. The role of fragment anisotropy as a useful probe of entrance channel effects at energies close to the barrier is pointed out.

Three-dimensional exact angular momentum projection is used to investigate the shape of transitional nuclei. It is found that in cases in which the unprojected energy surfaces are almost $\gamma$ unstable, angular-momentum-projected energy surfaces show pronounced minima having triaxial shapes, in which a large fraction of the wave function localizes in the region ${20}^{\circ }<~\gamma <~{40}^{\circ }$.

Angular distributions of massive fragments from relativistic heavy-ion interactions are reported. Sideward peaking is observed for the light fragment ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$, from 25-GeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + Au, while the distribution for ${}_{}{}^{127}{}_{}{}^{}\mathrm{Xe}$ is strongly forward peaked. Conflicts of these observations and other existing data with predictions of models for the fragmentation process are discussed.

The equation of state of nuclear matter is predicted in analogy with a universal form recently observed to hold for other self-bound systems. This approach was suggested by two findings. First, the spin-isospin-averaged realistic nucleon-nucleon interaction potential is observed to be of the universal form in the region of strong bonding. Secondly, a resulting relation between the cohesive and surface energy is shown to hold for nuclear matter as well as metals and the electron-hole liquid.

Radiation pressure from a laser has been used to cool and compress small nonneutral plasmas of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{+}{}_{}{}^{}$ ions confined by static electric and magnetic fields. A second laser has been used as a probe to measure ion densities of 2×${10}^7$ ${\mathrm{cm}}^{-3\mathrm{}}$ and ion temperatures below 100 mK. A Coulomb coupling constant, $\Gamma$, as large as 10 has been measured indicating that the plasma is strongly coupled. In the future, values of $\Gamma$ large enough to observe a liquid-solid phase transition should be accessible.

A series of pellet-fueling experiments has been carried out on the Alcator $C$ tokamak. High-speed hydrogen pellets penetrate to within a few centimeters of the magnetic axis, raise the plasma density, and produce peaked density profiles. Energy confinement is observed to increase over similar discharges fueled only by gas puffing. In this manner record values of electron density, plasma pressure, and Lawson number ($n\tau$) have been achieved.