A new class of realizations of the dynamical group O(4,2) depending on an arbitrary function $G$ is found. As a special case it is applied to a moving relativistic composite object which in its rest frame is a three-dimensional oscillator. The wave equation is exactly solved; the generators of the Poincaré group are identified. It can be applied to a moving "bag" or bound state where the constituents are bound by a confining potential. The form factors and structure functions are discussed.

Excitation functions ($E_{\mathrm{lab}}=235-320\mathrm{}$ MeV) for producing nuclei close to the compound system (evaporation residues) were measured for ${}_{}{}^{58,64}{}_{}{}^{}\mathrm{Ni}$+ ${}_{}{}^{112-124}{}_{}{}^{}\mathrm{Sn}$, corresponding to a 20% variation in the compound-nucleus neutron number. A dramatic, order-of-magnitude increase was observed in the maximum cross section as a function of the compound-nucleus neutron neutron excess. The subbarrier energy dependence of the cross sections is well described by an optical-model calculation, but not by the frequently used parabolic approximation.

By use of standard forms for the various interactions of a system of $N$ neutrons and $Z$ negative pions, it is shown that for a large variety of values of $N$ and $Z$ the system can become bound. This gives rise to a structure similar to that of an ordinary nucleus, but in which the protons are replaced by negative pions.

A Hamiltonian for $\pi$, $N$, and $\Delta$ is constructed from meson-exchange mechanisms. The $\mathrm{NN}$ interaction in the model is directly derived from the Paris potential. Good fits to $\mathrm{pp}$ scattering data up to 1 GeV, including the "resonant" ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}F_3^{}{}_{}{}^{}$ partial waves, have been obtained when a $\pi N\leftrightarrow \Delta$ interaction is introduced in a dynamical three-body approach. The model can be used for a many-body study of $\Delta$-nucleus dynamics.

A new, infrared-laser-spectroscopic method for in situ ion drift-velocity and mobility measurements in a dc glow discharge is reported, a method sensitive to quantum effects in the ion transport process. Excellent agreement with earlier drift-tube studies for the mobility of Ar${\mathrm{H}}^{+}$ in He is obtained. While no ion rotational energy dependence was observed in preliminary measurements, a vibrational dependence was suggested.

The construction of physical transition probabilities in non-Hermitian, effective-Hamiltonian models of multiphoton ionization is analyzed. Eigenstates of the effective Hamiltonians, $\hat{H}$ and ${\hat{H}}^{†}$, are respectively determined to be projected incoming and outgoing states. These models are found to be intrinsically $S$-matrix models, and the adiabatic eigenstates are used to construct appropriate transition amplitudes. The intermediate-time bound-electron population differs quantitatively from customary norm-of-state constructions.

This Letter reports experimental measurements of the velocity $v$ of a Taylor vortex front propagating into an unstable Couette state in rotating Couette-Taylor flow and of the wavelength selected by this dynamical process. The data are consistent with a constant velocity $v\propto {\epsilon }^{\frac{1}{2}}$, as predicted from an amplitude equation, but are nearly a factor of 2 smaller than that prediction. Recent dynamic experiments on the onset of Taylor vortex flow by Park, Crawford, and Donnelly are explained in terms of vortex-front propagation.

For a relativistic electron beam penetrating an unmagnetized plasma, a change is seen in the emission spectrum from $\omega \sim {\omega }_p$, $2{\omega }_p$ line emission to continuous $\omega \gg {\omega }_p$ emission, as $\frac{n_b}{n_p}\to 1$. High-power (of order megawatts per gigahertz) broadband radiation up to ∼100 GHz suggests collective Compton-boosting mechanisms in a new regime of superstrong turbulence. Highly directional emission and magnetic field dependence agree with this interpretation.

Superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ offers a unique example of level crossing, that of the zero-sound mode and the internal "real squashing" mode of the gap parameter. A full treatment of this classic problem is given which compares well with observations at 1.2 bars and 45 MHz. The characteristic beat pattern seen on-resonance is identified is identified as a "$0\pi$-area" pulse, first discussed by Crisp. The present findings for the signal velocity agree with Brillouin's well-known predictions.

Electrical-resistivity, magnetic-susceptibility, and specific-heat data reveal that U${\mathrm{Be}}_{13}$ is superconducting below 0.85 K. Highly anomalous low-temperature electronic properties in both the normal and superconducting states result in an enormous electronic specific-heat coefficient $\gamma =1.1\mathrm{}$ J/mole ${\mathrm{K}}^2$ and a corresponding magnetic susceptibility $\chi =1.5\mathrm{}\times {10}^{-2\mathrm{}}$ emu/mole. The superconducting state appears to be extremely stable with an initial slope of the temperature derivative of the critical field ${\left(\frac{\partial H_{c2\mathrm{}}}{\partial T}\right)}_{T_c}=-257\mathrm{}$ kOe/K.

Random point pinning of ideal or defective flux-line lattices is simulated on a computer. For weak pins, Larkin and Ovchinnikov's two-dimensional collective pinning is confirmed: $j_c=\mathrm{const}\times \frac{n_p〈{f_p}^2〉}{R_p{c}_{66}}$ ($j_c$ is the critical current; $n_p$, $f_p$, and $R_p$ are the density, force, and range of pins; and $c_{66}$ is the shear modulus). The constant is determined. Defective lattices are pinned more strongly by factors 1.3 to 3, explaining the observed history effect. A pronounced jump in the curves $j_c\left(f_p\right)$ indicates the onset of plastic deformation.

Voltage-current measurements of an amorphous indium/indium-oxide thin-film composite have yielded values for the exponent $\eta \mathrm{}\left(T\right)\mathrm{}$ describing the power-law decay of the order-parameter correlation function appropriate to the Kosterlitz-Thouless description of phase transitions in two-dimensional systems. A pronounced crossover in the characteristics at the phase-transition temperature is obtained. Theoretical expressions both above and below $T_c$ are verified, and a value of $\eta \left(T_c\right)=0.23\mathrm{}$ is measured for a film with normal-state sheet resistance of 3560 Ω/□ measured at 8 K.

Granular superconductors are shown to have a far-infrared absorption that is larger when the samples are superconducting than when they are normal. By contrast, theoretical models for these materials predict that when the samples become superconducting, the absorption should decrease.

Superconducting sampling circuits have been used to investigate the transient response of long indium microbridges to current pulses in excess of their critical currents. For the first time, the rising-edge kinetic inductance spike and the nonzero minimum voltage have been observed, as well as the delay time until the normal state appears. These results are in reasonable agreement with a detailed theoretical model of the experiment and yield an estimate of 140 ps for ${\tau }_E$, the inelastic scattering time, in indium.

Magnetic and Mössbauer measurements on a $\mathrm{Au}$-19-at.%-Fe alloy are reported. After ferromagnetic ordering at $T_c\cong 170$ K, spin-glass-like transverse ordering sets in below $T\cong 60$ K; strong irreversibility in the magnetization process only occurs below $T\cong 15$ K. This behavior is consistent with the predictions of a Heisenberg mean-field model, in which the transverse ordering transition is distinct from a crossover to strong irreversibility.

From the pressure dependence of the Néel temperature ($T_{\mathrm{N}}$) in Cr-Ge alloys, the antiferromagnetic transition is found to be to the commensurate state, when Ge is greater than 0.6 at.%. The present extended x-ray-absorption fine-structure study on Cr-Ge shows clearly that Ge goes substitutionally into the Cr lattice. On the basis of the rigidband model this can be understood only if Ge acts as an electron donor to the $d$ band of Cr. These findings raise the interesting question as to how Si and Ge additions stabilize the commensurate phase, despite their smaller $\frac{e}{a}$ ratio.

The combination of high energy and angle resolution (100 meV, ±3°) with spin analysis in photoemission spectroscopy is shown to allow the direct observation of magnetically spin-split electronic states. This is demonstrated for normal emission from Ni(110) with polarized Ne i radiation ($h\nu =16.85\mathrm{}$ eV). It is found that ${\Delta }_{\mathrm{ex}}=0.18\mathrm{}$ eV for the exchange splitting of the $S_4$ band at the $X$ point in good agreement with a band-structure and photoemission calculation that considers the self-energy correction explicitly.

Cooperative multiparticle quantum states in an Einstein-Podolsky-Rosen type of experiment are shown to violate a Bell inequality. Thus correlations can occur between wave packets each having $N$ bosons which cannot be explained within local hidden-variable theories. This provides a way to test quantum measurement theory for multiparticle states. In these states, a local, positive probability distribution exists for all $N$. However, the representation of correlations with this probability distribution is different from that in standard (Bell-type) hidden-variable theories.

A new algorithm for the simulation of statistical systems is presented. The procedure produces a random walk through configurations of a constant total energy. It is computationally simple and applicable to systems of both discrete and continuous variables.

The possibility of a long $B$-meson lifetime is explored, in which case the weak mixing angles ${\theta }_2$ and ${\theta }_3$ are quite small. This allows the derivation of a lower bound on the top-quark mass as a function of the $B$-meson lifetime, by comparison of the short-distance prediction for the $\mathrm{CP}$-nonconservation parameter $\epsilon$ with its experimental value. The bound is significant for ${\tau }_B>4\mathrm{}\times {10}^{-13\mathrm{}}$ s.