Rotating Superconductors and the Frame-independent London Equation

A frame-independent, thermodynamically exact London equation is presented, which is especially valid for rotating superconductors. A direct result is the unexpectedly high accuracy ($\sim10^{-10}$) for the usual expression of the London moment.Comment: 4 pages, 0 figure

Stresses in a quasi-isotropic pin loaded connector using photoelasticity

Birefringent glass-epoxy and a numerical stress separation scheme are used to compute the stresses in the vicinity of a pin-loaded hole. The radial and circumferential stresses at the hole edge, and the net section and shear-out stresses are computed. The numerical and experimental results are compared with the computed stresses. The fixture used to load the connector is discussed and typical isochromatic and isoclinic fringe patterns are presented. The stress-separation scheme is briefly discussed

Hardcore bosons on checkerboard lattices near half filling: geometric frustration, vanishing charge order and fractional phase

We study a spinless hardcore boson model on checkerboard lattices by Green function Monte Carlo method. At half filling, the ground state energy is obtained up to $28\times 28$ lattice and extrapolated to infinite size, the staggered pseudospin magnetization is found to vanish in the thermodynamic limit. Thus the $(\pi,\pi)$ charge order is absent in this system. Away from half filling, two defects induced by each hole (particle) may carry fractional charge ($\pm e/2$). For one hole case, we study how the defect-defect correlation changes with $t/J$, which is the ratio between the hopping integral and cyclic exchange, equals to $V/2t$ when $V\gg t$. Moreover, we argue that these fractional defects may propagate independently when the concentration of holes (or defects) is large enough

Selection of the SIM Astrometric Grid

We investigate the choice of stellar population for use as the Astrometric Grid for the Space Interferometry Mission (SIM). SIM depends on the astrometric stability of about 2000 stars, the so called Grid, against which the science measures are referenced. Low metallicity, and thus relatively high luminosity K giants are shown to be the population of choice, when available. The alternative, nearby G dwarfs, are shown to be suseptable to unmodeled motions induced by gas-giant planetary companions, should there be a significant population of such companions. Radial velocity filtering is quite efficient in selecting Grid members from the K giants with yields exceeding 50% if filtering at 30m/s (1-sigma) is available. However if the binary fraction of the G dwarfs approaches 100% as some studies suggest, the yield of stable systems would be in the range of 15% at best (with 10m/s filtering). Use of the initial SIM measurement as a final filter is shown not to be critical in either case, although it could improve the yield of stable grid members. For a Grid composed of weak-lined K giants, the residual contamination by large unmodeled motions will amount to about 3% (and rises to about 6% if a 60m/s radial velocity criterion is used). The selective introduction of quadratic terms in the proper motion solutions during the post-mission phase of data reduction can reduce contamination to a remarkable 1% or better in either case. Analytic estimates based on circular orbits are developed which show how these results come about.Comment: 42 pages including 13 eps figures. To be published Sept 2002 in PAS