We formulate information-theoretic Bell inequalities, which apply to any pair of widely separated physical systems. If local realism holds, the two systems must carry information consistent with the inequalities. Two spin-$s$ particles in a state of zero total spin violate these information Bell inequalities.

The detection rates in cryogenic detectors of neutralinos, the most well motivated supersymmetric dark-matter candidate, are calculated. These rates can differ greatly from the special case of pure photinos and pure Higgsinos which are usually considered. In addition, a new term is found in the elasticscattering cross section proportional to the $Z$-ino component which is "spin independent," even for these Majorana particles. As a result, substantial detection rates exist for previously disfavored, mostly spinless materials such as germanium and mercury.

I consider string propagation in a certain complexified version of space-time, in an attempt to gain some intuition about a possible unbroken phase of string theory. Topological σ models (related to Floer and Gromov theory) correspond from this point of view to the consideration of only strings with a selfdual pattern of momenta and windings. I also observe an amusing generalization of the high-energy saddle point studied by Gross and Mende; this generalization involves complex space-time and separate Riemann surface moduli for left-moving and right-moving modes.

Radiative Majorana masses for the three known neutrinos can be generated via the exchange of two $W$ bosons if there is a fourth neutrino with both Dirac and Majorana masses. Typical masses of the order ${10}^{-8\mathrm{}}$, ${10}^{-3\mathrm{}}$, and ${10}^2$ eV are obtained.

The electroweak model with one Higgs doublet is investigated when the mass of the Higgs particle is larger than the weak-interaction scale. It is shown that the SU(2) Higgs sector with spontaneously broken O(4) symmetry and perturbative gauge coupling becomes a trivial field theory at infinite cutoff. Around the trivial Gaussian fixed point, for finite cutoff, a low-energy effective theory is found with non-trivial couplings and mass generation from spontaneous symmetry breaking. We find an upper bound of $M_H\approx 640$ GeV on the mass of the Higgs particle with a lattice momentum cutoff $2\pi$ times larger than the Higgs-boson mass.

We investigate the production of hadronic jets with high transverse momenta $p_T$ at the forthcoming DESY $\mathrm{ep}$ collider HERA. We find that events where the exchanged quasireal photon is resolved into quarks and gluons dominate the two-jet cross section for $p_T\lesssim 40$ GeV. We also find that this class of events contributes about 20% to the total $b\overline{b}$ and $c\overline{c}$ production. The possibility to use these processes to measure the gluon content of the photon is discussed.

According to perturbative QCD, nuclear quasiexclusive reactions should be $\propto A^1$ at asymptotically large momentum transfer. Here we analyze how the asymptotic prediction is modified at finite energies by the expansion of the quark systems as they become hadrons and exit from the nucleus. We find that the phenomenon of nuclear transparency should be apparent in presently fesible experiments, but the degree of transparency is sensitive to the expansion model.

The two-electron process of simultaneous electron transfer and excitation (TE) in atomic collisions is studied within the close-coupling method for the example system ${\mathrm{He}}^{+}$+H. The calculated energy dependence of the population of various helium doubly excited states is analyzed for the role of electron correlations in the resonant and nonresonant contributions to the TE process which are included coherently. It is predicted that the impact-parameter-dependent state-selective TE probabilities show conspicuous peak structures.

A resonance Raman study of water has been performed with the use of excitation wavelengths ranging from 200 nm (6.20 eV) to 141 nm (8.78 eV). With excitation resonant with the dissociative $\tilde{A}$ state the spectra exhibit intensity exclusively in the symmetric stretching vibration, showing up to six quanta. There is no activity in the bending or antisymmetric stretching vibrations, showing that the dissociation of the $\tilde{A}$ state of water proceeds initially along the symmetric-stretch coordinate. Resonance with the second absorption band results in a spectrum exhibiting significant intensity in the bending vibration.

Intense laser fields in optical neutral-atom traps can have a profound effect on collision cross sections at ultracold temperatures, $T<\mathrm{}{10}^{-3\mathrm{}}$ K. A simple model is developed for the long-range interatomic potentials of two field-dressed atoms. Field dressing ensures that the cross section for associative ionization of two ultracold Na atoms is large in an optical trap, but the cross section is predicted to be about 4 orders of magnitude smaller in optical molasses.

Results from the first fully three-dimensional simulations of driven damped strong Langmuir turbulence and wave collapse are presented. Key results are that turbulence is maintained at least in part by nucleation, the cores of most collapsing objects are pancake shaped in form, and the power spectrum falls off approximately as the product of a power law and an exponential at large wave number.

We report preliminary dynamical structure-factor $G(q,t)\mathrm{}$ measurements performed on polydisperse polymer cluster solutions at concentrations such that the largest clusters are partly penetrated by smaller clusters. Upon increase of the polymer concentration, the $G(q,t)\mathrm{}$ profile goes from a stretched-exponential function, with an exponent which decreases as concentration increases, to a power-law function. These features suggest that the dynamical properties of this system exhibit glasslike behavior.

Atomic-beam diffraction and molecular-dynamics calculations have been combined to study the structures of overlayers of the dipolar molecules C${\mathrm{H}}_3$F and C${\mathrm{H}}_3$Cl physisorbed on bare and xenon-plated graphite crystals. On the former substrate, C${\mathrm{H}}_3$F adopts a commensurate triangular lattice with one molecule per unit cell, whereas on the latter the unit cell doubles. On both substrates C${\mathrm{H}}_3$Cl is incommensurate with antiferroelectrically ordered molecules arranged in a uniaxially distorted structure.

A new method of isothermal-isobaric molecular dynamics is developed to study the melting mechanism of a two-dimensional lattice with a piecewise-linear force law. Discontinuities in density and enthalpy upon melting and hysteresis upon cooling clearly mark the transition as first order. Analysis of atomic configuration snapshots reveal that melting begins with the formation of grain boundary clusters, as predicted by Chui, and is completed by successive unbinding of dislocations and disclinations.

The kinetics of ordering and coarsening in single-crystal ${\mathrm{Cu}}_3$Au are studied by use of time-resolved x-ray scattering. After a quenching from high temperatures to fixed temperatures below the order-disorder temperature, three regimes are apparent: nucleation, ordering, and coarsening. The superlattice peaks are anisotropic, reflecting the domain structure. The line shape of the scattering function changes with time during the crossover from the ordering to the coarsening regime. The late-stage coarsening is consistent with curvature-driven growth.

In an investigation of self-diffusion in bcc $\beta$-Ti single crystals by means of both quasielastic and inelastic neutron scattering, the elementary diffusion jump has been determined directly, and the lattice vibrations which trigger the jump have been elucidated. The elementary jump for self-diffusion is a simple ½ [111] jump into a nearest-neighbor vacancy. The reason for the anomalously fast self-diffusion is a fluctuation of $\omega$-phase type which facilitates jumps into neighboring vacancies.

The vacuum tunneling probe used in the scanning tunneling microscope represents a new class of nonreciprocal electromechanical transducers. Nonreciprocity implies reduced back action and consequently increased sensitivity over conventional, reciprocal transducers. A vacuum tunneling probe may reach the quantum limit for a measurement of the position of a macroscopic mechanical oscillator even with use of a non-quantum-limited amplifier. The quantum limit is enforced by the momentum shot noise associated with the tunneling current.

State-selective laser techniques are used to study the scattering of NO molecules on a crystallographic diamond surface. It is inferred that the diamond surface differentiates between "left" and "right" incoming molecules and accordingly endows them with different energy contents after the collision without providing any energy to them. Time-of-flight spectra show the existence of two velocity components in the scattered molecules that correspond to two different molecule-surface collision histories.

A new model for band offsets in lattice-matched heterojunctions is presented along with a novel definition of the interface dipole which avoids any reference to an ideal interface. The model is derived only from the charge densities of the bulk constituents and naturally predicts the independence of the offsets on interface geometry. It is in excellent agreement with accurate first-principles pseudopotential calculations for ${\mathrm{}\left(\mathrm{GaAs}\right)\mathrm{}}_3$/${\mathrm{}\left(\mathrm{AlAs}\right)\mathrm{}}_3$ grown in the (001), (110), and (111) directions and with available experimental data.

The density of states of a two-dimensional electron gas is calculated in the weak-disorder limit by taking into account self-consistent screening and Landau-level coupling effects. The resultant density of states is broad with considerable overlap between Landau levels, being strikingly different from the well-separated sharp levels of the standard short-range impurity-scattering model. In qualitative agreement with a number of recent experimental findings, calculated level broadenings are much larger than that implied by the zero-field mobility.