A gauge theory for the Lorentz connection of a space-time describes geometries of stars with variable parametrized post-Newtonian parameter $\gamma$; its value depends explicitly on the structure of a star: The value of $\gamma$ for a neutron star is different from that for the solar system ($\left|{{\gamma }_{\odot }}^{-1\mathrm{}}\right|<~{10}^{-2\mathrm{}}$). Because of the absence of a "local parity invariance" $\gamma$ is positive for ordinary stars and $\gamma$ is negative for sources of gravity consisting of antimatter.

We study systematically the high-energy behavior of backward Compton scattering and pair annihilation in massive quantum electrodynamics. For both of these processes (where a fermion is exchanged), we find, in the complex angular-momentum plane, a fixed cut with a simple pole coming out at a physical value of momentum transfer. These results are used to discuss possible behaviors, at extremely high energies, of hadronic processes with the exchange of quantum numbers.

Using the simple model that the amplitude for ${\eta }^{\prime }\to \eta \pi \pi$ is dominated by the $\delta \mathrm{}\left(970\right)\mathrm{}$ resonance we find a satisfactory fit to the data. The quadratic mass formula for $\eta -{\eta }^{\prime }$ mixing with a positive mixing angle (i.e. reduction of $s\overline{s}$ content in the physical $\eta$ state) is preferred in agreement with the requirement for ${\eta }^{\prime }\to 2\gamma$. Failure of the current-algebra calculation for ${\eta }^{\prime }\to \eta \pi \pi$ is explained and is shown not to be evidence against the (3*, 3) ⊕ (3, 3*) model of chiral-symmetry breaking.

Differential cross sections have been measured at Fermilab with a focusing spectrometer for ${\pi }^{\pm }p$, $K^{\pm }p$, and $p^{\pm }p$ elastic scattering at 50-, 70-, 100-, 140-, and 175-GeV/c incident momentum over the $\mathrm{}\left|t\right|\mathrm{}$ range 0.03 to 0.8 Ge${\mathrm{V}}^2$. The results are smooth in $t$ and are parametrized by quadratic exponential fits.

Using a quadrupole focused neutrino beam, 61 events with two muons in the final state have been observed at Fermilab. These include seven ${\mu }^{-}{\mu }^{-}$ events. A comparison of the event rate in two targets of different hadron absorption length indicates that attributing the events to $\pi$ or $K$ leptonic decay is ruled out by 4.0 standard deviations. No trimuon events were observed which, combined with lepton conservation, indicates an unobserved neutral lepton is present in most of the events.

Neutrino-induced dimuon events probably involve the production and subsequent decay of one or more real, intermediate particles. The observed properties of dimuon events are shown not to agree with the hypotheses that the intermediate particles are heavy leptons or semiweak vector bosons. This strongly suggests production of new hadrons as the leading explanation of dimuon events. Such new hadrons, decaying weakly, would necessarily possess a new, as yet unidentified, quantum number.

Suppose that a neutral, heavy, spin-½ lepton were created by a mixed neutrino-anti-neutrino beam incident on an arbitrary target and that this lepton subsequently decayed into a $\mu$ pair and a neutrino (or antineutrino). Then the ratio of the respective mean laboratory energies for the ${\mu }^{-}$ and ${\mu }^{+}$ lies between 0.48 and 2.10.

We have measured ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}(p, n){}_{}{}^{40}{}_{}{}^{}\mathrm{K}\left(\mathrm{antianalog}\right)$ differential cross sections at 24 MeV and made microscopic distorted-wave Born-approximation calculations for these cross sections. Unlike the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $t$) reaction to the same state, where it is necessary to invoke a two-step mechanism, the ($p, n$) data are fitted by the one-step calculation. A one-step calculation also fits ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}(p, n){}_{}{}^{40}{}_{}{}^{}\mathrm{K}\left(\mathrm{isobaric}\mathrm{analog}\right)$ data with the same nucleon-nucleon interaction used in the antianalog-state calculation.

It is argued that single-particle-like behavior in nuclear matter is much less probable than Brueckner theory suggests. In particular, the quasiparticle pole strength is evaluated for nuclear matter and it is shown that, contrary to the spirit of Brueckner theory, low-momentum states play a crucial role in determining the magnitude of $z_{k_{\mathrm{F}}}$.

Measurements have been made to check recent findings of fission-fragment energy variations in low-energy neutron resonances of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$. The result has been negative.

We have observed more than fifty peaks between 400 keV and 4 MeV in photoneutron spectra of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Transitions occur to the ground state and first two excited states of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ from discrete absorption features, some of which are less than 100 keV wide even above 11 MeV. Three states, the most prominent of which is at 9.034 MeV, under lie a controversial electron-scattering resonance, supporting an $E2\mathrm{}$ rather than $E0\mathrm{}$ interpretation.

The previously unexplained dependence of proton and deuteron inelastic scattering on the spin of the residual nucleus is shown, in an almost model-independent way, to result from scattering from the ground-state quadrupole moment.

A new measurement of the $g_J$ factor in the $2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ metastable state of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been made using an optical-pumping technique. Our result is $\frac{g_J({}_{}{}^4{}_{}{}^{}\mathrm{He}, 2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{})}{g_J({}_{}{}^1{}_{}{}^{}\mathrm{H}, 1{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{})}=1-23.15\mathrm{}\left(10\right)\mathrm{}\times {10}^{-6\mathrm{}}$. This value agrees with theory and provides confirmation of a recent atomic-beam measurement. Further doubt is cast on an earlier optical-pumping determination, thereby resolving a possible discrepancy between theory and experiment.

A self-consistent constant longitudinal electric field is shown to exist in a collisional electronic cold plasma through which a circularly polarized plane wave is propagating. This electric field arises from the displacement of the electrons from the immobile ions and constitutes a return force which exactly balances the forward Lorentz force due to the collisions.

A collision-dominated inhomogeneous plasma seeded with a distribution of impurity grains is calculated to fill out rapidly with random megagauss fields for temperatures of about a kilovolt. Possible applications of this phenomenon (i) to enhance relativistic-electron-beam coupling to low-$Z$ target plasmas, (ii) to influence transport coefficients, or (iii) to localize $\alpha$-particle deposition in a reacting DT plasma are discussed.

Neutron-inelastic-scattering measurements have been performed on liquid La, Ce, and Pr. The results demonstrate that a well-defined "crystal field" exists in liquid rareearth metals and that the scattering can be understood if it is assumed that the crystalfield potential is uniaxial.

An exact result is derived for the coefficient $B_{\mathrm{xc}}$ which determines the first gradient corrections to the exchange and correlation energy of an inhomogeneous electron gas. A method of approximation, which is based on the random-phase approximation and is exact at high density, is given for the explicit evaluation of $B_{\mathrm{xc}}$. Numerical results are also given for the metallic density range and applications are discussed.

We investigated the clean surface fo a Pt(100) single crystal in its stable (5 × 20) and metastable (1 × 1) configurations by ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction. The photoelectron spectrum of the (1 × 1) surface for $h\nu =11.6-40.8\mathrm{}$ eV is characterized by a narrow peak 0.25 eV below the Fermi level; it is suggested that this peak is due to a maximum in the surface density of states associated with an electronic surface resonance or surface state on the (1 × 1) surface.

We present a simple model for the magnetic susceptibility of rare-earth compounds which exhibit interconfiguration fluctuations (ICF). It is shown that the temperature dependence of the magnetic susceptibility of several ICF Yb compounds can be fitted quantitatively, assuming an energy separation $E_{\mathrm{ex}}$ between the two configurations and an intrinsic lifetime $\tau$ due to the $4f$-shell-conduction-electron interaction. With the parameters $E_{\mathrm{ex}}$ and $\tau$ obtained from such fits it is possible to predict the temperature dependence of the valence.

By standard arguments, observed hydromagnetic waves in the Crab Nebula imply an upper limit to the photon rest mass of $\mu \lesssim {10}^{-16\mathrm{}}-{10}^{-15\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $m_{\mathrm{ph}}\lesssim 3\times {10}^{-54\mathrm{}}-3\mathrm{}\times {10}^{-53\mathrm{}}$ g (uncertainty < factor 100), smaller than the previous best limits by a factor ${10}^4$-${10}^5$. However, the standard wave arguments used here and elsewhere are reexamined and found not to be rigorous, although the limits given are probably valid in order of magnitude.