All the equilibrium states of the two-dimensional Ising system are convex combinations of the pure phases and, as such, translation invariant. This has been rigorously proven and is related to the instability of phase boundary lines with respect to thermal fluctuations. While in higher dimensions stable phase coexistence is known to occur, the instability is expected to be typical of two-dimensional systems.

We have observed a prompt single-muon signal in the region $0.8<\mathrm{}{p}_t<2.5\mathrm{}$ GeV/c produced by the interactions of 400-GeV protons in steel. The prompt $1-{\mu }^{+}$ rate is comparable in magnitude to the prompt $2-\mu$ rate in the same kinematic region. If interpreted as originating from the production and muon decay of charmed particles, the $1-\mu$ signal corresponds to a charm production cross section in the range of 13 to 60 μb/nucleon, depending on production parameters.

We report on a search for the photoproduction of $D^0\left({\overline{D}}^0\right)$ mesons in events which have zero total visible strangeness. We observe an enhancement of 94±19 events in the $K^{\pm }{\pi }^{\mp }$ decay mode, corresponding to a cross section of ∼720 nb assuming a branching ratio of 0.018.

The origin of the universe as a quantum phenomenon leads to a self-consistently generated space-time structure in which the mass of the created particles is $O\left({\kappa }^{-\frac{1}{2}}\right)$. We interpret the origin of the universe as a phase transition in which the grand unified symmetry is spontaneously broken.

Differential cross sections and analyzing powers have been measured for elastic and inelastic scattering of 800-MeV protons by ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Microscopic analyses utilizing the impulse approximation are used to study the ground-state neutron distribution of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and to demonstrate the importance of the spin-orbit amplitudes for the inelastic transitions.

Measurements are reported of the spherical tensor component $t_{20}$ for 1.0-, 0.8-, and 0.4-GeV equivalent proton bombarding energies for elastic $p-d$ scattering between 155°-175°. They are very close to zero in disagreement with the predictions of nucleon exchange models, including the Kerman-Kisslinger model with $N^{*}$ components in the deuteron wave function. The experiment was performed with a vector- and tensor-polarized deuteron beam scattered from a liquid hydrogen target.

A search has been made for an anomalously heavy isotope of oxygen spanning the mass range 20 to 54 amu with use of a tandem accelerator as an ultrasensitive mass spectrometer. An upper limit of heavy hadron to nucleon ratios was established at ${10}^{-16\mathrm{}}$ over the entire mass region and over a large portion of it at ${10}^{-18\mathrm{}}$. This ratio is considerably lower than the predictions of cosmological models, namely ∼${10}^{-10\mathrm{}}$ to ${10}^{-11\mathrm{}}$.

The results of the first measurements of the velocity dependence of the total ionization ${\sigma }_I$ and the total destruction ${\sigma }_d$ (ionization+excitation+deexcitation) cross sections for fast Rydberg-atom-neutral-molecule collisions are presented. The observed resonant structure in and the absolute magnitudes of ${\sigma }_I$ and ${\sigma }_d$ unambiguously confirm the prediction that the Rydberg electron bound to a fast atom scatters quasifreely. The data also strongly hint that the ionic core does the same.

The results of pseudopotential calculations of the interaction of an alkali atom with its rare-gas neighbors in a solid matrix are presented. They can explain an interesting effect which appears to be due to optical pumping between two equilibrium positions in a bistable trapping site.

A slow-wave structure was used to launch electron plasma waves traveling preferentially in one direction. The current generated by the waves was observed. The magnitude of the current can be estimated from momentum conservation in the wave-particle interaction process.

Experiments show that axial confinement of plasma in a straight theta-pinch solenoid is improved by placing solid lithium deuteride plugs at the ends. The energy confinement is increased nearly threefold in agreement with theoretical estimates which assume classical electron thermal conduction and no convective losses. The confinement of deuterium ions is explained by classical Coulomb collisions in the ablated lithium deuteride plasma.

We report the experimental observation and theoretical description of a previously unrecognized mechanism for electromagnetic emission from plasmas near the geometric mean plasma frequency. Very clear emissions were observed from the electric-field-dominated NASA Lewis bumpy torus plasma at a frequency which is inconsistent with familiar mechanisms of plasma emission. A theory based on a Penning-discharge-like beam-plasma interaction predicts a frequency in excellent agreement with the observations.

In the RECE-Christa device, electron rings were adiabatically compressed in low-density background gas with axial magnetic field compression ratios $\frac{B_{\mathrm{zf}}}{B_{\mathrm{zi}}}\lesssim 4$, without encountering any gross instabilities or other anomalous losses. In agreement with a simplified theoretical model, the field-reversal factor, $\delta$, remains constant, and the major radius and the axial length of the rings scale with ${B_z}^{-\frac{1}{2}}$ while the ring current increases with ${B_z}^{\frac{1}{2}}$. Furthermore, field-reversal times have been extended to 1.1 msec.

We consider the effects of the superconducting state upon the ultrasonic properties of metallic glasses at low temperatures. A number of measurable effects are predicted. Their observation would confirm the influence of conduction electrons upon two-level systems in these materials.

The statistical mechanics of the polymer poly(vinylidene fluoride) are studied by means of a formalism in which interchain and intrachain forces derived from conformational analysis are combined in a transfer-integral approach through a mean-field approximation. The theory is successful in yielding several observed phases of this material and in predicting the effect of uniaxial stress on the most stable phase.

The adsorption of Cs on Cu(111) produces major changes in the Cu $3d$-band part of angle-resolved photoelectron spectra recorded at $\hslash \omega =16.8\mathrm{} \mathrm{and} 21.2$ eV. The angular dependence is much reduced and the spectra are quite similar to those obtained from polycrystalline Cu. We associate this behavior with a strong incoherent scattering by the adsorbate.

The magnetic susceptibilities of powdered samples of ${\mathrm{Me}}_4$NCu${\mathrm{Cl}}_3$ (TMCuC) and [(C${\mathrm{H}}_3$)${}_3{}^{}{}_{}{}^{}\mathrm{NH}$]${}_3{}^{}{}_{}{}^{}\mathrm{Cu}_2^{}{}_{}{}^{}$${\mathrm{Cl}}_7$ (TTMCuC) have been measured. Both compounds behave like one-dimensional $S=\frac{1}{2}$ Heisenberg ferromagnets which are weakly coupled antiferromagnetically to adjacent chains. For TMCuC, we obtained $\frac{J}{k}=30\mathrm{}$ K with $\left|J^{\prime }\right|\lesssim 0.003$ K; the ratio $\left|\frac{J^{\prime }}{J}\right|$ is the lowest yet found for a ferromagnetic $S=\frac{1}{2}$ chain. For TTMCuC, we obtained $\frac{J_{\mathrm{FM}}}{k}=50\mathrm{}$ K, with $\left|\frac{J^{\prime }}{J_{\mathrm{FM}}}\right|\lesssim {10}^{-4\mathrm{}}$, and $\frac{J_{\mathrm{AFM}}}{k}=-10\mathrm{}$ K for the antiferromagnetic chains also present.

The linewidths of long-wavelength longitudinal and intermediate-wavelength transverse phonon resonances of a two-dimensional Wigner lattice are calculated. The dominant scattering is umklapp scattering involving ripplons, which is restricted by the large mean square displacement of the electrons. The dependences of the linewidths on density, temperature, and phonon wave vector are very different from that in the gas, and large variations in the linewidths are predicted near the melting temperature for small holding fields.

The sensitivity of NASA's Deep Space Network spacecraft tracking system to an isotropic cosmological background of gravitational radiation is analyzed. It is found that by using the autocovariance function of the Doppler record in the so-called "three-way" tracking mode to dig into the noise it is possible to put significant limits on this background with current and future planned deep-space missions.

We present high-statistics results on the reactions $a+p\to c+X$ where $a$ and $c$ can be any of ${\pi }^{\pm }$, $K^{\pm }$, $p$, or $\overline{p}$. The data were taken at 100 and 175 GeV/c incident momenta using the Fermilab Single-Arm Spectrometer operated over the kinematic range $0.2<x<\mathrm{}1.0\mathrm{}$ and $p_t<~1.0$ GeV/c. Investigating the $x$ dependence of the data, we find agreement with a quark-parton picture, namely the cross sections have a power-law behavior in $1-x$ independent of $p_{\mathrm{beam}}$ and $p_t$.