Microwave radiation is observed from electrically biased semiconducting BiSb alloys. The radiation emitted from ${\mathrm{Bi}}_{92}$${\mathrm{Sb}}_8$ and its harmonics to the fourth order are very narrow band and coherent. The mechanism of emission is postulated to be a super-radiant maser effect due to transitions between paramagneticlike levels pumped by the electric current.

Because of the near perfect local satisfaction of the valence requirements of each atom, which is complemented by the positional and compositional disorder, covalently bonded amorphous alloys are intrinsic semiconductors. We describe a band model with some novel features, which successfully describes several important effects observed in these amorphous semiconducting alloys.

Quantum statistics of one-photon interaction of light with matter is investigated. It is found that in general the density operator changes. For a chaotic field, however, the density operator changes only in a trivial way.

The generic, nonrotating, homogeneous cosmological model for a closed space (Bianchi type IX) has a very complex singularity which can, however, be described in detail. It appears that only the exceptional (previous studied) cases will have particle horizons. Thus these models may lead to some insight into how the broad-scale homogeneity of the universe may have been produced at very early times.

We have observed ∼3000 examples of the reaction ${\pi }^{+}d\to \mathrm{pp}{\pi }^{+}{\pi }^{-}{\pi }^0$ and report on ∼300 events in which the ${\pi }^{+}{\pi }^{-}{\pi }^0$ mass is in the ${\omega }^0$ mass region and ∼40 events in the ${\eta }^0$ mass region. Differential cross sections are presented. There is evidence for a backward peak in the overall channel. We give values for the ${\omega }^0$ density-matrix elements in the forward direction. Our value for $\mathrm{Re}{\rho }_{10}$ is negative, in disagreement with various theoretical models.

It is suggested that the amplitude for virtual Compton scattering at large spacelike photon masses is completely dominated at all energies by the Pomeranchukon exchange or diffraction mechanism and that all the contributions of $s$-channel $N^{*}$ resonances and "ordinary" $t$-channel exchanges decrease rapidly with $q^2$. Experimental and theoretical implications of this conjecture are discussed.

The CERN phase-shift analysis is used to evaluate the left-cut term of the $P_{11}$ partial wave of pion-nucleon scattering. The inelastic $\frac{N}{D}$ equation is solved with this term and the elasticity $\eta$ as input. The output and input phase shifts agree below 2 BeV if and only if at least two Castillejo-Dalitz-Dyson poles are included in the canonical $D$ function. This result rules out single-channel bootstrap models and furnishes a constraint on many-channel models.

The temperature dependence of both the isotropic and anisotropic parts of the Knight shift in cadmium is calculated and found to be in good agreement with experiment. Lattice vibrations effectively decrease the strength of the lattice potential and make it more isotropic. As the temperature increases the energy bands become thus more free-electron-like and the $s$ character of the wave functions on portions of the Fermi surface increases. At the same time the cancellation due to different $p$ contributions in the various sheets of Fermi surface is destroyed, and the anisotropy also increases.

Low-$q$ phonons cause local distortions of the crystal lattice which cause the gaps in the electronic band structure to wobble up and down. This results in a broadening of the peaks in low-energy electron diffraction which otherwise would be much narrower than observed, according to recent calculations. The effect varies with temperature and energy as $T^{\frac{1}{2}}{E}^{\frac{3}{4}}$ in rough agreement with experiment.

An anomaly, apparently a final-state spin dependence, has been observed in proton inelastic scattering from ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$, and ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}$. The excited-core model of inelastic scattering cannot produce such an effect. Indeed, no current theory of inelastic scattering based on the distorted-wave Born approximation can even qualitatively predict such an effect.

The differential cross section for elastic scattering of 10.83-MeV photons by Pb and by U has been measured for scattering angles between 20° and 150°. The elastic scattering has been resolved from inelastic contributions for the first time. For scattering angles less than 45° this process is dominated by the Delbrück effect.

A sizable number of $\alpha$ particles were detected at 18.8° in $p$-BeO collisions at 28.5 BeV. The alpha-to-deuteron ratio is found to be of the order of 1% for secondary momenta below 1000 MeV/c per nucleon. Possibilities of obtaining secondary alpha beams at high-energy accelerators for various experiments, in particular those relevant to the study of the origin and propagation of cosmic rays, are discussed.

Quasielastic scattering of neutrinos, $\nu +n\to p^{+}+{\mu }^{-}$, was measured in a 30-ton spark-chamber detector. Analysis of the cross section versus momentum transfer yields a value of $M_{A_1}=0.7\mathrm{}\pm 0.15$ for a single-pole-type axial-vector form factor or $M_{A_2}=1.05\mathrm{}\pm 0.2$ for a double-pole form factor. No decrease in cross section at low momentum transfer expected due to nuclear effects was observed.

We examine the experimental basis for the generally accepted statement that lingering $2\pi$ decays from a neutral kaon beam imply that $\mathrm{CP}$ invariance must be abandoned. We find that, apart from formulations which cannot be distinguished physically from theories admitting $\mathrm{CP}$ noninvariance, no $\mathrm{CP}$-invariant description seems possible within the context of quantum theory. If quantum mechanics is disregarded, $K^0$-decay experiments do not necessarily contradict $\mathrm{CP}$ invariance. A crucial test is proposed for that case.

Possible empirical coupling regularities for baryons on Regge trajectories are indicated.

How to express superconvergence relations for pion scattering as statements about the generators $X_a$ of chiral SU (2) ⊗ SU (2) is shown. One of the superconvergence relations has a remarkable algebraic significance: The matrix $m{J}_y$ (where $m$ and $\overrightarrow{\mathrm{J}}$ are the mass and spin matrices) is the sum of a chiral scalar and the fourth component of a chiral four-vector.

We propose a new method which summarizes in closed compact form all the implications of analyticity in a problem with broken symmetry. This method is applied to the Bethe-Salpeter equation to obtain the broken-$\mathrm{SL}\mathrm{}(2,C)\mathrm{}$ results for the Regge daughter trajectories in a closed functional form:

$\alpha _k^{}{}_{}{}^{(\pm )}+k=F(t,t{(\alpha _k^{}{}_{}{}^{(\pm )}+\frac{1}{2})}^2,\pm E^{2M}(\alpha _k^{}{}_{}{}^{(\pm )}+M\left)\right(\alpha _k^{}{}_{}{}^{(\pm )}+M-1\left)\cdots \right(\alpha _k^{}{}_{}{}^{(\pm )}-M+1\left)\right)$

where $F$ is an analytic function in three variables.

We have measured the spectrum, intensity, and polarization of light Raman scattered from rotons and higher energy quasiparticle excitations in liquid ${\mathrm{He}}^4$ for temperatures between 1.16 and 2.14°K. The effect on the spectrum of the temperature-dependent energy and lifetime of the rotons is clearly visible. At a scattering angle of 90° the light is highly depolarized and about three orders of magnitude weaker than the Brillouin scatering from the phonons.

Results of an experimental study of fluctuations of an unstable weakly ionized magnetoplasma with no axial drift is reported. Correlation measurements indicate that the observed waves propagate primarily in the azimuthal direction and that the parametric dependence of the phase velocity on pressure and magnetic field seem to be similar to that expected for a drift wave. The waves appear to be nonlocal in nature, the characteristic azimuthal and radial-mode numbers being unity.

Experimental results show that the small-scale filaments in liquid, obtained with a single-mode laser, are composed of continuous series of focal spots. Many related observations are shown to be consistent with the picture of moving foci.