An illustration of sliding contact at any constant speed on highly elastic half-spaces

A rigid smooth indentor slides at a constant speed on a compressibleisotropic neo-Hookean half-space that is subjected to pre-stressaligned with the surface and sliding direction. A dynamic steady-slidingsituation of plane strain is treated as the superposition ofcontact-triggered infinitesimal deformations superposed uponfinite deformations due to pre-stress. The neo-Hookean materialbehaves for small strains as a linear elastic solid with Poisson'sratio 1 : 4. Exact solutions are presented for both deformationsand, for a range of acceptable pre-stress values, the infinitesimalcomponent exhibits the typical non-isotropy induced by pre-stress,and several critical speeds. In view of the unilateral constraintsof contact, these speeds serve to define the sliding speed rangesfor which physically acceptable solutions arise. A Rayleighspeed is the upper bound for subsonic sliding, and transonicsliding can occur only at a single speed. For the generic parabolicindentor, contact zone traction continuity is lost at the zoneleading edge for trans- and supersonic sliding. For pre-stresslevels that fall outside the acceptable range, either a negativePoisson effect occurs, or a Rayleigh speed does not exist andthe unilateral constraints cannot be satisfied for any subsonicsliding speed. Received 15 March 2000. Revised 22 November 2000.     

Earthquakes and circle packings

We prove that earthquakes on hyperbolic surfaces can be approximated by discrete earthquakes constructed using circle packings. Consequently, we obtain a combinatorial version of Thurston’s Earthquake Theorem. Any surface can be approximated by combinatorial earthquakes of a packable surface. This provides a controlled combinatorial method for deforming hyperbolic surfaces.     

Asymptotics of Weil�CPetersson Geodesics II: Bounded Geometry and Unbounded Entropy

We use ending laminations for Weil–Petersson geodesics to establish that bounded geometry is equivalent to bounded combinatorics for Weil–Petersson geodesic segments, rays, and lines. Further, a more general notion of non-annular bounded combinatorics, which allows arbitrarily large Dehn-twisting, corresponds to an equivalent condition for Weil–Petersson geodesics. As an application, we show theWeil–Petersson geodesic flow has compact invariant subsets with arbitrarily large topological entropy.     

On Convergence Approach Spaces

The extension of two axioms due to Cook and Fischer to the category CAP of convergence approach spaces leads to the study of non-Archimedean approach spaces as well as two versions of regularity appropriate to CAP and related categories.     

Search for universal extra dimensions in pp collisions

We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a pp center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R(-1)>260 GeV in a minimal UED model.     

Measurements of WW and WZ production in W + jets final states in pp collisions

We study WW and WZ production with ?νqq (?=e,μ) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb(-1) of integrated luminosity from pp collisions at sqrt[s]=1.96 TeV. Assuming the ratio between the production cross sections σ(WW) and σ(WZ) as predicted by the standard model, we measure the total WV (V=W,Z) cross section to be σ(WV)=19.6(-3.0)(+3.2) pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure σ(WW)=15.9(-3.2)(+3.7) pb and σ(WZ)=3.3(-3.3)(+4.1) pb, which is consistent with the standard model predictions.     

Resonant holographic interferometry for species concentration measurements with saturated anomalous dispersion

A double-exposure resonant holographic interferometry measurement technique for full-field, instantaneous species is presented. This technique utilizes tuned pulsed dye lasers, separate reference beams, and a corrective holographic optical element. The resulting interferogram fringes represent the species number density of interest with variations in the bulk refractive index due to the temperature field automatically subtracted. Expressions for relating resonant absorption with fringe shift are disclosed. The relations suggest that RHI is well suited for optically dense media and long path lengths, where absorption measurements can be difficult. A saturation related modification of the dispersion near a broadened resonant transition is described. The depopulation of the ground state due to saturation by the probe beam causes an asymmetric modification of the resonant refractive index, which when convolved over the probing beam does not affect the measured fringe shift as measured by RHI. Resonant interferometry is demonstrated as an accurate and quantitative measure of the concentration of sodium vapor in a low pressure cell. Furthermore, as a combustion diagnostic, RHI is demonstrated on a minor combustion species, OH, in a nonpremixed slot burner. PACS 33.70-w; 42.40.Kw; 82.33.Vx     

Multilayer thin-film inspection through measurements of reflection coefficients

A vibration-insensitive interferometer is described to measure the thickness, refraction index and surface profile of thin-film stack at normal incidence. By satisfying the continuous boundary conditions of electric and magnetic fields at interfaces in a multilayer film stack, the reflection coefficient phase of the thin-film stack can be distinguished from the phase of spatial path difference, thus thickness and refraction index can be extracted. The experiment results showed that the measurement precision is significantly increased after the phase analysis was added into the reflectance analysis.