We evaluate the electric and magnetic polarizabilities of the proton and neutron in chiral perturbation theory to one-loop order. We present a detailed discussion of the polarizabilities in the chiral limit. Our calculation explains the experimentally observed patterns concerning the relative magnitudes of the electric and magnetic polarizabilities of the proton and the neutron. We also point out the need for a higher-loop calculation to include important resonance exchanges.

In order to investigate the coupling between collective flow of nucleons and pions in hot pion-dominated hadronic matter, we calculate the pion-nucleon drag coefficient in linearized transport theory. We find that the characteristic time for flow equalization is longer than the time scale of the expansion of a hardonic fireball created in high-energy collisions. The analysis of transverse-momentum data from p+p¯ collisions at √s =1.8 TeV reveals the same flow velocity for mesons and antinucleons. We argue that this may be evidence for the formation of a quark-gluon plasma in these collisions.

The detectability of collective transverse flow is discussed for CERN superproton synchrotron energies in Pb+Pb collisions. Calculations with a quark-gluon string model suggest there will be measurable flow in Pb+Pb reactions but not in S+S reactions at 160 GeV. Calculations of transverse flow with a fluid-dynamic model show a strong dependence on the equation of state and that the amount of flow is significantly larger than in the string model.

Multifragment disintegrations following ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$${+}^{197}$Au collisions at E/A=50 MeV have been studied with a multidetector system covering 88% of 4π in solid angle. The average number of intermediate-mass fragments (Z=3–20) increases strongly as a function of charged-particle multiplicity and reaches values larger than six for the most violent collisions. The results are compared to calculations with both dynamical and statistical models.

High-resolution I 4d photoelectron spectra (total instrumental resolution <0.06 eV) of several iodine molecules, ICl, IBr, ${\mathrm{I}}_2$, and ${\mathrm{Ch}}_2$${\mathrm{I}}_2$, are reported. The inherent I 4d Lorentzian linewidths increase in the above order, due to the decrease in electronegativity of the moieties bound to I. The ligand-field splitting as measured by the ${\mathit{C}}_2^0$ crystal-field term decreases in the above order, and correlates extremely well with the electric-field gradient measured by ${}_{}{}^{129}{}_{}{}^{}\mathrm{I}$ quadrupole splittings.

Here, we propose and analyze a technique for active suppression of tokamak edge turbulence. Suppression occurs due to the effects of a sheared radial electric field generated by externally driven radio-frequency waves. Plasma flow is induced by radially varying wave-driven Reynolds and magnetic stresses, and opposed by neoclassical damping. For Alfvénic flow drive, the predicted shear flow profile is determined by ion inertia and electron dissipation effects. Results indicate that a modest amount of absorbed power is required for edge-turbulence suppression. More generally, several novel results in the theory of momentum transport by electromagnetic fluctuations are presented.

A scanning tunneling microscopy and spectroscopy study of the recombinative desorption of hydrogen from the Si(100)-2×1 surface is presented. Initially at room temperature, hydrogen atoms singly occupy the Si dimer units while at higher temperatures (∼630 K) these atoms tend to pair up. This pairing phenomenon is due to a π-bonding interaction which favors pairing individual dangling bonds on the dimer units. Following desorption from the saturated surface, pairs of dangling bonds are found loaalized on the Si dimer units. The significance of these paired-dangling-bond sites is d)scussed in ligh* of the desorption model recently proposed by Sinniah et al.

With the low-energy-electron projection microscope it has been possible to image the lattice of thin gold films with atomic resolution. A theory modeling the coherent point source as the origin of a spherical wave is capable of describing both the Gabor-type holograms as well as the automatically resolved lattice images of the gold films.

We report photoluminescence and resonant-Raman-scattering studies of single GaAs/AlAs quantum-well structures. Splittings of the exciton peaks show that there is a large-scale island structure at the interfaces. Shifts in the absolute exciton energies of quantum wells grown at different substrate temperatures and also the form of the optical-phonon energies as a function of both mode index and quantum-well width indicate that there also exists a small-scale structure on the interfaces.

Interface dynamics are analyzed theoretically in the quasilocal regime of directional growth explored by experiments on liquid crystals. We discover ‘‘vacillating-breathing’’ (VB) modes. Upon variation of the growth speed the interface motion enters a chaotic regime via a quasiperiodicity scenario. Chaos occurs as a complex interplay between VB and parity-broken traveling modes. We suggest that the quasiperiodicity scenario should be generic for systems where these two modes coexist.

We provide the first experimental test of the universality of a surface amplitude ratio near a critical end point by measuring the modified critical adsorption amplitude ratio, ${\mathit{R}}_{\mathit{M}\mathit{A}}$, for the liquid mixtures aniline+cyclohexane and isobutyric acid+water. Our results thus far support the universality hypothesis with ${\mathit{R}}_{\mathit{M}\mathit{A}}$=1.3±0.1. The universality of ${\mathit{R}}_{\mathit{M}\mathit{A}}$ would imply that the surface tension amplitude ratio Q is universal in agreement with the predictions of Fisher and Upton; however, a precise connection relating ${\mathit{R}}_{\mathit{M}\mathit{A}}$ to Q is not currently available.

The ac conductivity σ(ω) of three ionically conducting crystalline materials (${\mathrm{NaClZn}}^{2+}$, ${\mathrm{KTaO}}_3$:${\mathrm{Co}}^{3+}$,${\mathrm{H}}^{+}$, and ${\mathrm{CeO}}_2$:${\mathrm{Gd}}^{3+}$) and two glasses have been studied over an unusually wide temperature range. In all cases, limiting power-law behavior [exponent s=1 in σ(ω)=${\mathrm{\sigma }}_0$+A${\mathrm{\omega }}^{\mathit{s}}$] is observed at relatively low temperatures. It is concluded that this limiting behavior is a universal phenomenon. Available theoretical explanations have been examined and found to be unsatisfactory.

We have investigated both the structures and the excitation spectra produced by submonolayer adsorption of potassium on the surface of graphite at 90 K, using high-resolution low-energy electron diffraction in conjunction with high-resolution electron-energy-loss spectroscopy. We show that at very low coverages a dispersed potassium phase is formed with a giant K-K spacing (around 60 Å); this phase continuously compresses with increasing adatom density until a critical coverage where a close-packed structure nucleates. Below the critical coverage, charge is redistributed between the alkali and the substrate to increase the frequency of the substrate plasmon mode; above the critical coverage, excitations attributed to metallic potassium are observed.

Liquid Ar submonolayers physisorbed on graphite have been studied by ellipsometry. The layers have been evaporated by means of laser pulses and the time evolution of the coverage upon readsorption has been studied as a function of temperature (T<${\mathit{T}}_{\mathit{c}}$) and bulk gas pressure.

We study the process of monopole-antimonopole (hedgehog-antihedgehog) annihilation in nematic liquid crystals theoretically and experimentally. We show, using a ‘‘mini-max’’ argument, that there exists a stable scaling solution to the nematodynamic equations describing this phenomenon, and find the solution numerically. We study the process experimentally in the uniaxial nematic, 4-cyano-4’-n-pentylbiphenyl, following a pressure jump or thermal quench. We confirm, over 3 orders of magnitude in time, the scaling-solution prediction for the pair separation D. We find D∝(${\mathit{t}}_0$-t${)}^{\mathrm{\alpha }}$ with α=0.5±0.03.

The drag force (per unit length) acting on a steadily moving disclination line is calculated. The problem is formulated in two equivalent ways: One involving a linear partial differential equation but with ambiguous boundary conditions, and another involving a nonlinear equation but with uniquely defined boundary conditions. The second formulation is solved numerically; the results of the numerical simulation are then used to fix the boundary conditions for the first formulation, which is solved analytically. A finite value is obtained for the drag force, without a need to introduce the integration cutoff at the sample size.

We report observations of the instability of Taylor-Couette flow of helium II. The results are in substantial agreement with recent calculations of Barenghi and Jones using the full modern equations of the flow of helium II. This result is the first instance of success of a linear-instability theory with the equations of helium II and is the strongest evidence available that the equations of motion and the boundary conditions used in the analysis are correct.

For the first time, latent tracks induced by swift Kr ions have been directly observed in mica. These tracks are imaged by atomic-force microscopy as hollows which are associated with softer areas in the mica surface. The track core is formed by disordered mica. The mean diameter of the observed hollows increases with the electronic stopping power of the ions. The track shape along the ion path is deduced from the analysis of both the number of the tracks per unit area and their diameter distribution. These observations are the first images of nanometric changes of elastic properties.

Nonergodicity parameters, the nondecaying components of the coherent intermediate scattering functions, of ‘‘hard-sphere’’ colloidal glasses were measured by dynamic light scattering. These agree reasonably well with the predictions of mode-coupling theory for hard-sphere atoms, with no adjustable parameters in the comparison. In addition, we provide further verification of the recently developed theory of dynamic light scattering by nonergodic media.

Self-fracturing of solids during chemical transformations is considered, and a first quantitative model of this widespread phenomenon is proposed. The analysis begins by considering the equilibrium of a single crack, and proceeds with the behavior of an ensemble of cracks. This enables one to solve the ‘‘selection problem’’ for this pattern-formation process and obtain formulas for the rate of crack-network propagation and for the diameter of the resulting blocks.