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Udo Schelb 《International Journal of Theoretical Physics》1997,36(6):1341-1358
The paper is concerned with the derivability of a Lorentz instead of only a Weyl manifold as space-time structure from postulates
about free fall and light propagation. For this purpose it identifies a property distinguishing both kinds of space-times.
The property is one of a particular metric of the conformal class of the Weyl manifold. viz. that in suitably chosen locally
geodesic coordinates theg
i4 components,i=1, 2, 3 vanish along the time axis. Although seemingly somewhat hidden, one is led to this property in looking for a metric
which can play a distinguished role. We demonstrate that for a Lorentzian manifold such a condition is always given; thus
it is a necessary one. It is sufficient since for a Weyl space it has the consequence that the metric connection of the selectedg is projectively equivalent to the Weyl connection. Thus, if a Weyl space-time complies with it, it is a reducible one. The
results of this paper lay the ground for deriving in a second step this condition from a simple, empirically testable postulate
about free-fall worldlines and “radar” measurements by light signals. 相似文献
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The microwave part of the dielectric spectrum (ν ? 1 GHz) is considered of aqueous phospholipid solutions in the limit of high water content. A continuum model is presented which allows to calculate in the water relaxation region the frequency-dependent complex permittivity of solutions in which the bilayers form globular single-walled vesicles as well as multilamellar liposomes. The model is not only capable of explaining the strikingly small values of the extrapolated static permittivity and of the main dielectric relaxation time which became evident in many measurements on colloidal aqueous solutions of phospholipids. It also allows the positive and negative step-like changes in the dielectric properties of solutions, which have been found at the main (order-disorder) phase transition temperature of the bilayers, to be explained by dimensional changes as resulting from vesicle growth and fusion. 相似文献
110.
Soils developed from recent basalts of Marion Island in the Sub-Antarctic contain about 20% of a poorly crystalline iron oxide. The association of this phase with Al and Si appears to have a major influence on its Mössbauer spectra: whereas room-temperature spectra indicate a relatively regular structure, the magnetic hyperfine fields at 4.2K are lower than those of even the most poorly crystalline pure ferrihydrites. 相似文献