Whether one uses a solar-system barycentric frame or a geocentric frame when including the general theory of relativity in orbit determinations for near-Earth satellites, the results should be equivalent to some limiting accuracy. The purpose of this paper is to clarify the effects of relativity in each frame and to demonstrate their equivalence through the analysis of real laser-tracking data. A correction to the conventional barycentric equations of motion is shown to be required.

There is a widespread intuitive belief that lattice theories are automatically ultraviolet finite. It is shown here that this is false and that lattice theories are not immune from ultraviolet infinities. This is illustrated with an example. Causes, cures, and lessons are briefly noted.

A search for pair production of fourth-generation sequential leptons in $e^{+}{e}^{-}$ annihilation at a center-of-mass energy $\sqrt{s}=56\mathrm{}$ GeV is reported. Event topologies corresponding to the cases where one particle decays leptonically while the other decays hadronically as well as those where both particles decay hadronically were explored. We set a 95%-confidence-level lower limit of 27.6 GeV/${\mathit{c}}^2$ for the mass of a fourth-generation lepton.

A search for sequential charged leptons decaying into massive neutrinos has been performed at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=56\mathrm{}$ GeV at the KEK colliding-beam accelerator TRISTAN. We have found no evidence for the production of the charged heavy leptons for an integrated luminosity of 5.3 ${\mathrm{pb}}^{-1\mathrm{}}$. A search for stable charged leptons was also conducted yielding null results. A new mass limit on the charged heavy leptons was obtained as a function of the mass of the associated neutrinos.

From the interactions of a deuteron beam in a liquid-hydrogen target at energies near the $d+p\to {}_{}{}^3{}_{}{}^{}\mathrm{He}+\eta$ threshold, $\eta$ events were selected on the basis of the momentum-analyzed ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ with a background of less than 2%. This opens the way to a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-tagged $\eta$ beam at Saturne, with a possible flux of ${10}^4$-${10}^5$ $\eta \text{'}\mathrm{s}$ per pulse. The present data allow an evaluation of the cross section down to less than 0.5 MeV above threshold. The deuteron tensor analyzing power $t_{20}$ has also been measured: The small negative value found at threshold (-0.15 ± 0.05) seems incompatible with models based on one-pion exchange.

The first triple-coincidence data resulting from pion absorption in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are reported. The existence of a three-nucleon absorption component in the four-nucleon channel is established. A four-nucleon phase-space-like contribution and nucleon-nucleon final-state interactions are also identified.

In a spectroscopic study of the backward-angle yield from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+ ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at 3-4 times the Coulomb barrier, we find a strong preference for natural parity transitions in the excitation of close-to-yrast rotational bands. This selectivity is in strong quantitative disagreement with Hauser-Feshbach calculations for a compound-nuclear reaction and provides evidence for the conservation of the dinuclear parentage.

We describe the loading of a minimum-$B$-field trap with neutral atomic hydrogen cooled through thermal exchange with liquid-helium surfaces. We monitor the gas during filling and decay by observing the atoms which are ejected from the trap as a result of spin exchange and magnetic dipolar relaxation. The stability of the gas is unaffected if we change the wall coverage from pure ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to dilute ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixtures. The maximum trapped density is 3 × ${10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$ at about 100 mK. The limiting decay rate is attributed to dipolar relaxation and found to agree with theory for both magnitude and field dependence.

A gas of hydrogen atoms, confined in a static magnetic trap, has been evaporatively cooled to temperatures of a few millikelvin. The initial trap configuration held the gas at 38 mK for as long as 5 h. Evaporative cooling reduced the temperature to 3.0 mK while maintaining the central density at 7.6×${10}^{12}$ ${\mathrm{cm}}^{-3\mathrm{}}$. These values were determined by measurement of the rate of electronic spin relaxation and are in agreement with model calculations. Further cooling to 1 mK (inferred from the model) has been achieved. Measurements were made of the efficiency of the evaporative cooling process.

We study the behavior of atomic hydrogen in a monochromatic radiation field of high frequency $\omega$ and high intensity $I$, when its structure depends only on the parameter ${\alpha }_0=I^{\frac{1}{2}}{\omega }^{-2\mathrm{}}$ a.u., and when multiphoton ionization is quenched. At large ${\alpha }_0$ the ground-state binding energy undergoes a drastic reduction. This is coupled to an unprecedented stretching of the (oscillating) electron wave function, culminating in its separation into two parts (dichotomy) for ${\alpha }_0>50\mathrm{}$ a.u.

A nonperturbative method for describing the response of an orientational Kerr medium to arbitrarily strong electromagnetic fields is presented. The method is used to analyze recent phase-shift measurements for the static birefringence and new measurements for the time response of a suspension medium as functions of millimeter-wave intensity. Excellent agreement between theory and experiment provides the effective parameters in terms of which the nonlinear optical properties of the medium are assessed for applications to the millimeter-wave regime.

Shadowgraph flow-visualization studies and heat-flux measurements were used to study convection subjected to temporal modulation of the Rayleigh number $R$ in the form $\epsilon \mathrm{}\left(t\right)=\frac{R\left(t\right)\mathrm{}}{R_c^{\mathrm{stat}}}-1={\epsilon }_0+\delta sin\left(\omega t\right)$, where $R_c^{\mathrm{stat}}$ is the unmodulated threshold, and $\omega$ and $t$ are scaled by the vertical thermal diffusion time. For $\omega =15\mathrm{}$ and $0.7\lesssim \delta \lesssim 2.0$ the predicted hexagonal patterns were observed for a range of ${\epsilon }_0$ immediately above the convective threshold ${\epsilon }_c$. With increasing ${\epsilon }_0$ there is a region exhibiting coexistence between hexagons and rolls, followed by roll-like patterns. The observed boundaries between these regions and the magnitude of the convective heat transport are consistent with theory.

We examine theoretically the structure and properties of index gratings created by the interference pattern formed by a laser beam and a surface polariton at an interface coated with a thin layer of an optical Kerr material. Theory suggests that the energy-transfer characteristics of these gratings differ considerably from those created in the bulk material. This statement is underscored by a the prediction that energy transfer will occur for degenerate beams in the presence of a nonlinearly responding reflecting surface even though there is no photorefractive material present.

We observe Doppler shifts of a CIII impurity line in a spheromak plasma showing toroidal rotation during the formation phase of the spheromak configuration but not during the equilibrium or decay phase. The evolution of the velocity fields is consistent with the estimated rate of cross-helicity decay given the viscosity and resistivity of the plasma.

Energy absorption in the edge region via cyclotron harmonic interaction during plasma heating with the ion-cyclotron range of frequencies is examined. It is shown that the electric field ripple caused by the closely spaced Faraday-shield conductors gives rise to large effective perpendicular wave numbers, resulting in strong cyclotron harmonic damping. For the parameters of the ASDEX tokamak, carbon impurity ions with $Z=5\mathrm{}$ and an initial perpendicular energy of 1 eV could be accelerated to energies in excess of 1 keV in less than 10 μs (corresponding to about 100 cyclotron orbits).

We have performed a set of prototypical quantum calculations of the electronic structure of a nine-atom helium plasma over wide ranges of temperature and density. These calculations reveal the presence of very tightly bound quasimolecular states in high-density plasmas, even at temperatures high enough to ionize fully the component atoms. The results of the study suggest that there are four regimes in a plasma, dependent upon the relationship of the electron wavelength to the interionic spacing: low-density atomic, intermediate-density screened atomic, high-density quasimolecular, and very-high-density homogeneous.

The macroscopic behavior of a restricted liquid has been studied through ultrasonic velocity and attenuation measurements utilizing a picosecond colliding-pulse optical technique. Transparent porous sol-gel glasses allowed a study of the collective fluid dynamics as a function of confining pore radius and temperature. The acoustic response of the supercooled state was found to be strikingly different from that of any ordinary liquid, and consistent with a simple model.

A new kind of localized mode is proposed to occur in a pure anharmonic lattice. Its localization properties are similar to those of a localized mode for a force-constant defect in a harmonic lattice. These modes, which are thermally generated like vacancies but with much smaller activation energies, may appear at cryogenic temperatures in strongly anharmonic solids such as quantum crystals as well as in conventional solids.

Inelastic neutron-scattering experiments have been performed for the first time on glassy phosphorus-selenium alloys. The effective density of vibrational states so obtained is highly structured in the case of glassy ${\mathrm{P}}_{0.67}$${\mathrm{Se}}_{0.33}$ and provides evidence for the existence of molecular clusters in the structure based predominantly on ${\mathrm{P}}_4$${\mathrm{Se}}_3$ units, i.e., a "zero-dimensional" glass.

The complete set of acoustic-mode frequencies associated with elastic constants in cerium fluoride have been measured by Brillouin scattering to temperatures of about 1500 K. These frequencies decrease linearly from 300 to about 1150 K. Above 1150 K striking deviations from linear behavior are observed. The results are discussed in terms of anharmonicity and a diffuse superionic transition in which the development of disorder proceeds by means of cooperative mechanism.