122 research outputs found
On the metric structure of space-time
I present an analysis of the physical assumptions needed to obtain the metric
structure of space-time. For this purpose I combine the axiomatic approach
pioneered by Robb with ideas drawn from works on Weyl's "Raumproblem". The
concept of a Lorentzian manifold is replaced by the weaker concept of an "event
manifold", defined in terms of volume element, causal structure and affine
connection(s). Exploiting properties of its structure group, I show that
distinguishing Lorentzian manifolds from other classes of event manifolds
requires the key idea of general relativity: namely that the manifold's
physical structure, rather than being fixed, is itself a variable
Comptonization, the X-ray-radio correlation and the long-term periodicity in the chi-states of GRS 1915+105
We analyzed 139 chi-state observations of GRS 1915+105 with RXTE from 1997 to
2000 and found i) that the observations fall into two groups with different
Comptonization behavior, ii) that the slope of the hard X-ray component
correlates with the radio flux, thus revealing the interaction of jet and
corona, and iii) a 590 days long term periodicity in the hard X-ray and radio
components.Comment: 4 pages, 3 figures, Proceedings of the 4th Microquasar Workshop,
2002, eds. Durouchoux, Fuchs, & Rodriguez, published by the Center for Space
Physics: Kolkat
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