52,166 research outputs found
Note on generalised connections and affine bundles
We develop an alternative view on the concept of connections over a vector
bundle map, which consists of a horizontal lift procedure to a prolonged
bundle. We further focus on prolongations to an affine bundle and introduce the
concept of affineness of a generalised connection.Comment: 17 page
Static and Dynamic Pressure Distributions in a Short Labyrinth Seal
As part of a study into turbine blade tip destabilizing forces, a seals test rig was built in which spin rate, circular whirl rate, direction and amplitude of inlet swirl angle, and eccentricity can all be controlled over wide ranges, and measurements can be made at gap Reynolds numbers up to about 2 x 10(exp 4). This facility is described and preliminary data is presented for a one cavity labyrinth seal with a flat, stator mounted land. The impact of different flow coefficients for the first and second knives on the rotordynamic coefficients was found. While this effect is dominant for the direct forces, it should also be incorporated into calculations of cross forces where it has an impact under many conditions
New measurements of magnetic fields of roAp stars with FORS1 at the VLT
Magnetic fields play a key role in the pulsations of rapidly oscillating Ap
(roAp) stars since they are a necessary ingredient of all pulsation excitation
mechanisms proposed so far. This implies that the proper understanding of the
seismological behaviour of the roAp stars requires knowledge of their magnetic
fields. However, the magnetic fields of the roAp stars are not well studied.
Here we present new results of measurements of the mean longitudinal field of
14 roAp stars obtained from low resolution spectropolarimetry with FORS1 at the
VLT.Comment: 5 pages, accepted for publication in A&
Kruskal coordinates as canonical variables for Schwarzschild black holes
We derive a transformation from the usual ADM metric-extrinsic curvature
variables on the phase space of Schwarzschild black holes, to new canonical
variables which have the interpretation of Kruskal coordinates. We explicitly
show that this transformation is non-singular, even at the horizon. The
constraints of the theory simplify in terms of the new canonical variables and
are equivalent to the vanishing of the canonical momenta. Our work is based on
earlier seminal work by Kuchar in which he reconstructed curvature coordinates
and a mass function from spherically symmetric canonical data. The key feature
in our construction of a nonsingular canonical transformation to Kruskal
variables, is the scaling of the curvature coordinate variables by the mass
function rather than by the mass at left spatial infinity.Comment: 18 pages, no figure
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