The TiN(001) surface phonons are studied by the Green's-function method. The electron-phonon interaction is described by the coupling of the electronic charge-density deformations to the nuclear displacements. Anomalies in the surface dispersion curves are found at half the distance to the boundary of the Brillouin zone in the [100] direction. The calculated surface density of states is in good agreement with that measured by Rieder and Drexel. It is suggested that the investigation of surface-phonon anomalies permits us to check the validity of bulk dynamical models.

Vacancy formation on the GaAs(111) surface is calculated to be strongly exothermic in character. The creation of one vacancy in each 2×2 cell allows the remaining Ga surface atoms to have a large inward relaxation, resulting in a 2.3-eV reduction in energy. It also transforms the polar (111) surface into a nonpolar (110)-like surface. The calculations provide strong support for the vacancy model of Tong et al., which is determined from analysis of low-energy-electron-diffraction data.

The specific heat in the superconducting state of U${\mathrm{Be}}_{13}$ shows marked deviations from BCS theory and obeys a $T^3$ rather than an exponential law at low temperatures. A good description is obtained by the assumption of an Anderson-Brinkman-Morel $p$-wave superconducting state at all temperatures. The value of the spin-fluctuation parameter deduced is large and consistent with the stability of such a state.

Momentum-resolved photoemission spectra from Cu(100) exhibit structure at 4 eV above the Fermi energy in a bulk band gap. This emission is pinned to the vacuum level and shows a free-electron-like dispersion. It is polarized with electric vector normal to the surface. The emission intensity is independent of the sample temperature unlike that of a simultaneously observed bulk direct transition. These properties identify the observed phenomenon as transitions into image-potential surface states.

Rydberg-like surface states are identified at Au(100) and Cu(100) surfaces by use of inverse photoemission with tunable photon energy. The binding energy (0.6 eV below vacuum) and width (≤ 0.3 eV full width at half maximum) of the $n=1\mathrm{}$ state agree well with previous calculations. Theory yields the expectation that these states represent a widespread phenomenon at surfaces.

The electronic polarizability of small metal particles is investigated within the framework of the local-density approximation applied to the spherical jellium model. Self-consistent effective potentials are used for the determination of the independent-particle susceptibility ${\chi }^0(\overrightarrow{\mathrm{r}},{\overrightarrow{\mathrm{r}}}^{\prime };\omega )$. On the basis of this ${\chi }^0$ the self-consistent field response equation, determining the susceptibility $\chi (\overrightarrow{\mathrm{r}},{\overrightarrow{\mathrm{r}}}^{\prime };\omega )$ of the interacting electrons, is solved with the inclusion of exchange and correlation. In this way we obtain for the first time the self-consistently determined absorption spectrum of small metal clusters.

An explicit expression is derived for the quantum gravitational vacuum state by use of the saddle-point approximation and a conformally invariant action. It consists of a superposition of zero-energy classical vacua that differ in the topology both of the local Lorentz frames (leading to $\mathrm{CP}$ nonconservation) and of space itself. Space is found to have Planck-size wormholes and spinorial knots, and is surrounded by a vapor of disconnected submanifolds. The scattering matrix constructed on this vacuum is not unitary but the superscattering matrix conserves probability.

We consider a new Lie-algebraic framework for the Pöschl-Teller potential, in which a single [$\mathrm{sp}\mathrm{}(2,R)\mathrm{}$ Casimir] operator has both bound and scattering states. This approach allows the determination of the $S$ matrix by purely algebraic means.

We introduce a scalar field in eleven-dimensional supergravity through the dual transformation of the totally antisymmetric torsion. All supersymmetries are spontaneously broken by the scalar field and the remaining four-dimensional Einstein space corresponds to anti-de Sitter space. The holonomy group of the seven-dimensional compact manifold is found to be an SO(7) subgroup of the original SO(8).

In the Gell-Mann-Levy $\sigma$ model, although the soliton by itself is unstable to collapse, the author finds a stable self-consistent solution of a valence (single-particle) nucleon bound state in a soliton (hedgehog) configuration of the meson fields. This solution has baryon number 2 and in the neglect of quantum fluctuations its energy is found to be less than $m_N=g〈\sigma 〉 (=g{f}_{\pi })$, the mass of the usual plane-wave nucleon.

A new and relatively simple theory of channeling radiation by ultrarelativistic particles, based on synchrotron radiation, yields promising results. The theory incorporates important quantum electrodynamic corrections, and provides detailed predictions of enhanced radiation.

The pure SU(4) Yang-Mills theory is studied at finite temperature. We observe a first-order transition at $\frac{8}{{g_c}^2}=10.50\mathrm{}\pm 0.02$.

It is shown that for a magnetic monopole in an SU(2) gauge theory, interacting with an arbitrary number of massless doublets of fermions, the global and the local conservation laws of the full four-dimensional theory, together with the restrictions on the fermions to $J=0\mathrm{}$ partial wave, uniquely determine the final state for a given initial state. As a result, monopole-induced baryon-number nonconservation is a necessary consequence of the conservation laws of the system. The modification of the conservation laws in the presence of the full SU(5) gauge interactions is discussed.

The differential cross section for the reaction $p\mathrm{}(n,d)\mathrm{}\gamma$ has been measured for angles between ${\theta }_d=0\mathrm{}°$ and ${\theta }_d(\mathrm{c}.\mathrm{m}.\mathrm{})=65\mathrm{}°$ at a neutron kinetic energy $T_n=185\mathrm{}$ MeV. On the assumption of time-reversal invariance, our results are in agreement with the deuteron photo-disintegration measurement at ${\theta }_p=0\mathrm{}°$ performed by Hughes et al. at Mainz. At present there exists no calculation for this reaction which is in satisfactory agreement with our measurements. The disparity between theory and experiment in this basic process, therefore, poses a persisting problem.

The charge, mass, and energy spectra of clean binary-fission events of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ projectiles at energies up to 1 GeV/nucleon are presented. The inelastic interaction cross section and the cross section for the production of binary fission (50% of all interactions) are found to be constant over the entire energy range.

We report the first measurement of Na and ${\mathrm{Na}}^{+}$ autoionization spectra following collisions of 1-MeV ${\mathrm{He}}^{+}$ ions on selectively excited $\mathrm{Na}3p{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ target atoms. The atomic states were populated with a cw dye laser which was tuned to the $\mathrm{Na}3s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\to \mathrm{Na}3p{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ transition. The simultaneous laser- ion-beam excitation technique produces significant intensity variations particularly for the decay of the ${\mathrm{Na}}^{+}2s2p^{6}3s{}_{}{}^{1,3}{}_{}{}^{}S$ and the ${\mathrm{Na}}^{+}2s2p^{6}3p{}_{}{}^{1,3}{}_{}{}^{}P$ states. The technique may provide additional information for line identification, excitation mechanisms, and angular distribution measurements.

An approximation to the Coulomb propagator, correct to first order in $\hslash$, is derived. This function has the structure $K=F(\lambda ,\mu ,\nu )\exp \left[iS\right(\lambda ,\mu ,\nu \left)\right]$, in terms of auxiliary variables $\lambda$, $\mu$, $\nu$ introduced in the solution of the corresponding Hamilton-Jacobi equation.

Studies of different types of transitions to chaos in Rayleigh-Bénard convection in a cylindrical container of mercury subjected to a horizontal magnetic field are reported. As the field is increased, structural changes of the spatial pattern are connected with different time-dependent behaviors and routes to chaos.

A new, first-principles derivation of the equations for a quantized single-mode laser field pumped by a semiclassical stochastic field in a four-level molecular pumping scheme is presented. Computer simulations are used to generate fits to measured correlation functions for a single-mode dye laser.

The formation of an ion-acoustic-type double layer was observed in the laboratory for the first time. The rarefactive part of a long-wavelength ion-acoustic wave grew in amplitude because of the presence of drifting electrons. The corresponding current limitation led to the formation of the double layer.