It is shown that QCD puts constraints on the value of the zero intercept of the leading non-Pomeron Regge trajectory. The inputs of the present analysis are the valon model of hadrons, some phenomenological properties of structure functions, and perturbative QCD. The result is ${\alpha }_{\rho }\mathrm{}\left(0\right)=0.40\mathrm{}\pm 0.04$.

The question is raised whether sensible light-hadron spectroscopy can be done on the small lattices used in recent analyses. Straightforward arguments together with the results obtained from a high-order hopping-parameter expansion and from quantum mechanical studies for heavy quarks indicate an answer: no.

The invariant differential cross sections and polarization ($0.5<\mathrm{}{x}_{\mathrm{F}}<0.8\mathrm{}$, $0.0<\mathrm{}{p}_{\perp }<1.5\mathrm{}$ GeV/c) of $\Lambda \text{'}\mathrm{s}$ produced in pion-induced reactions have been measured. The scaling cross section agrees with previous experiments performed at other energies. The ${(1-x_{\mathrm{F}})}^N$ dependence of the cross section gives an exponent of $N=1.88\mathrm{}\pm 0.04$. These are the first polarization measurements in the pion fragmentation region. A mean polarization of (-5.3 ± 1.2)% is observed with no trend toward large negative polarization with increasing transverse momentum.

A grand unified model is proposed which incorporates a "peculiar" photon in addition to the familiar photon. The model is constructed to reconcile the possible observations of fractional charges and monopoles. One way to have the weak-mixing-angle prediction agree with the phenomenological value is to require the peculiar photon to couple more strongly than the regular photon.

It is shown that the new proton resonance data on targets $A\sim 48$ provide a crucial check on the validity of direct reaction theory, viz. the existence of amplitude correlations between channels. These are often large ($\left|\rho \right|>~0.5$) and are not simply related to width correlations. Analysis with a simple reaction model shows that the large correlations must imply some failure of the distorted-wave Born-approximation theory of direct reactions.

Empirical conjectures of Feneuille, based on new regularities observed in the quasi-Landau spectrum, are investigated. Scaling laws for Rydberg atoms in magnetic fields are obtained from Schrödinger's equation, in two different approximations. Our formulas support the empirical conjectures and show them to be closely connected with the dynamics of the electronic motion in the $z=0\mathrm{}$ plane.

Absolute wave numbers have been measured to 2-3 parts in ${10}^9$ for the $2{}_{}{}^3{}_{}{}^{}S\to 4{}_{}{}^3{}_{}{}^{}S, 5{}_{}{}^3{}_{}{}^{}S, 4{}_{}{}^3{}_{}{}^{}D, \mathrm{and} 5{}_{}{}^3{}_{}{}^{}D$ two-photon transitions and the $2{}_{}{}^3{}_{}{}^{}P\to 3{}_{}{}^3{}_{}{}^{}D$ one-photon transition in helium. With use of relativistic calculations, Lamb shift values for these energy levels are derived and compared to theory. With improvements of one to two orders of magnitude in the theoretical calculations, these measurements could provide a new value for the Rydberg constant with an accuracy of 2 parts in ${10}^9$.

Coherence-preserving collisions for optical radiator-perturber scattering are studied by means of a velocity-selective photon-echo technique, using ytterbium atoms as heavy, long-lived, two-level radiators. These experiments establish the quantum diffractive nature of the radiator velocity change by demonstrating quantitative agreement with calculations. Radiator-destruction cross sections obtained with use of both Lamb dip and echo techniques agree to within 10%.

With use of a merged electron-ion beam apparatus, a lower limit of dielectronic recombination cross section for ${\mathrm{C}}^{+}\left({}_{}{}^2{}_{}{}^{}P\right)+e$ has been obtained from 9.04 to 9.32 eV. The measured cross section exceeds the theoretically predicted value by more than a factor of 3. This lies well outside the stated experimental and theoretical uncertainties.

Dielectronic recombination has been directly observed with use of crossed beams of electrons and ${\mathrm{Mg}}^{+}$ ions. Measurements were made of delayed coincidences between the stabilizing photon near 280 nm and the resultant neutral atom, and cross sections were determined. Theoretical cross sections are more than a factor of 5 smaller than those measured.

Transitions among states in wavy-vortex flow with different numbers of vortex pairs have been studied. The present observations are accounted for by a model which assumes that there are compressive and expansive limits to the size of the vortex pairs. The observations and the model show how more than one state can exist at the same Reynolds number.

A new measure of strange attractors is introduced which offers a practical algorithm to determine their character from the time series of a single observable. The relation of this new measure to fractal dimension and information-theoretic entropy is discussed.

Measurements of the frequency dependence of the microscopic second-order nonlinear electronic susceptibility are reported for the organic system $p$-nitroaniline. The results are suitably described in terms of a theoretical microscopic mechanism involving highly charge-correlated electron states dominating the second-order nonlinear optical response of the system as presented in earlier theoretical calculations.

Wave packets of electromagnetic or Langmuir waves trapped in a well between oscillating reflectors are considered. An equation for the temporal evolution of the probability distribution for the carrier wave number is derived, and solved analytically in terms of moments in the limits of long and short wavelengths. The relevance of the results for self-generated stochasticity for harmonically oscillating reflectors is point out, and the physical implications of the results are discussed.

An elastic neutron-scattering study of the "saturated" graphite compound K${\mathrm{C}}_8$ under hydrostatic pressure up to 20 kbar reveals two reversible staging transitions which require an increase of K in-plane density relative to the usual 2 × 2 superlattice. Between 15 and 19 kbar a mixture of integral stage-1 ($\dots \mathrm{C}M\dots$) and fractional stage-$\frac{3}{2}$ ($\dots \mathrm{C}M\mathrm{CC}M\dots$) stacking sequences is observed. The fractional staging confirms theoretical predictions of its existence in systems with long-range interlayer repulsion.

A high-resolution acoustic impedance technique has been used to investigate the collective-mode spectrum of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ near $T_c$. A new collective mode of the order parameter has been observed. The temperature at which the new mode appears is frequency, pressure, and magnetic field independent. The observed temperature dependence is very close to the predicted behavior of the super-flapping mode in the weak-coupling limit of the Anderson-Brinkman-Morel energy gap.

A recent treatment of superfluid turbulence is extended to the study of turbulence in a channel. It is found that as the flow velocity is reduced, a critical velocity is reached such that the rate at which new vortex singularities are created by line-line reconnections becomes insufficient to balance the loss of vortices at the channel walls, and the vortex tangle ceases to be topologically self-sustaining. Comparison with experiment indicates that this approach provides a reasonable explanation of observed critical velocities.

Low-energy electron diffraction from the copper (111) surface contains fine structure which is correlated with the emergence of beams in the metal. It is found that the fine structure determines points on the inner potential versus energy curve with virtually no dependence on surface relaxation. Postulating that the absorption of electrons is relatively weak in the ion cores, the authors present a low-energy electron-diffraction theory which predicts that electrons can channel through the ion cores of the layers parallel to the surface.

The technique of computer simulation is used to reveal a new and unsuspected phenomenon of the molecular liquid state which is observable by several different spectroscopic techniques. The phenomenon is explained in terms of the effect of a molecule's rotation on its own translation (or vice versa). This is directly measurable in optically active molecules, and exists for all molecules in the liquid state.

On the basis of a new first-principles, electronic model for the forces driving clustering and short-range order in metallic alloys, it is argued that observed concentration-dependent peaks in the x-ray and electron diffuse scattering intensities are due to parallel sheets of flat Fermi surface. The positions of the peaks are directly related to the spanning vector ${\overrightarrow{\mathrm{k}}}_0$.