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jrtomCERN: General relativity vs. exotic dark matter
Summary: it appears that it may not be necessary to assume the existence of "dark matter" in order to explain certain astronomical observations.
Includes a link to the actual paper on the LANL preprint archive.
Summary: it appears that it may not be necessary to assume the existence of "dark matter" in order to explain certain astronomical observations.
Includes a link to the actual paper on the LANL preprint archive.
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No God necessary...
Date: 10 October 2005 18:10 (UTC)Mmmmm, unnecessary assumptions.
figures /. checks their sources huh?
Date: 10 October 2005 20:54 (UTC)It looks like Cooperstock and Tieu may have forgotten a boundary term. What they believed is just a coordinate singularity turns out, upon reexamination, to be an unadvertised infinitely thin sheet of matter which contributes to the overall gravitational field.
I haven't worked through either of these papers carefully yet, but I plan to do so. This all came up at INPA tea this afternoon, and frankly, I haven't touched GR in far too long. I think the paper would simply have been buried had /. not touched it. And of course everyone on there is all like I knew that imaginary dark matter crap wasn't real!
One of the counterposts did bring up something I would have everyone remember as well: Measurements of the cosmic microwave background can be used to place constraints on the amount of non-luminous matter in the universe. The CMB provides a physically independent check from galactic rotation curves, and those results agree with similar results from gravitational lensing surveys and from surveys of the large-scale clustering of galaxies. Dark matter -- and specifically cold (nonrelativistic) dark matter -- is still needed to explain the formation of observed structure in the universe, because the structures that formed on the very largest scales all formed before densities of collapsing structures started to cross into the nonlinear regime of gravitational interaction. So if this treatment is correct, it'll have to explain all that as well as the rotation curves.
Re: figures /. checks their sources huh?
Date: 10 October 2005 21:00 (UTC)um...um...um...it's, uh, quintessence! yeah! that's it!
Thanks for the sanity check. :)