Talk:Kerr-Newman metric
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I'd like the new article to be called "Kerr-Newman electrovacuum". See the new "Exact solutions in general relativity" category to see why.---CH (talk) 02:46, 27 July 2005 (UTC)
- I don't see from the category or the article Exact solutions in general relativity why this should be renamed, but I also don't think I would understand your reply if you explained it. I do however know a fair bit about naming conventions, so I may be able to help. - Taxman Talk 19:25, August 3, 2005 (UTC)
Comments moved in from Kerr-Newman which has been merged here:
If I ever get around to creating the proposed infobox template for describing explicit examples of exact solutions, the surviving page should be modified to use the template. ---CH
[edit] Defining terms
The article defines Q and J but much of the rest is left up to imagination. Could someone knowledgable define these clearly?
- M is mass, Q is electrical charge (both having geometric units of length) and J is angular momentum (which has geometric units of area). If you encounter a, that is a=J/M, specific angular momentum (which has geometric units of length).
- You should think of these as measured at large distances by observers who are not moving with respect to the object at the center of the coordinate system. A subtle point is that because of the nonlinearity of gtr, there is an important distinction between local notions of mass (as measured by any observer anywhere, using any of various methods) and the former notion, which is a global notion of mass. Thus for example if a static observer near the hole compares the inward rocket engine thrust he must exert to maintain his position (so that he is accelerating outward with respect to test particles he drops at any time) with Newtonian theory, he would estimate a "mass" which differs from place to place depending on his position. This feature shows up the remarkable symmetries of the Ernst vacuum solutions to which the Kerr vacuum solution belongs. The Ernst family contains all stationary axisymmetric vacuum solutions to the Einstein field equation (a generalization also includes a possible electromagnetic field).
- This will no doubt be confusing. Unforunately (see next section), I won't be able to follow up.
[edit] Students beware
This article concerns a topic dear to my heart, and I had been monitoring it for bad edits, and had planned to greatly improve it, but I am leaving the WP and am now abandoning this article to its fate.
Just wanted to provide notice that I am only responsible (in part) for the last version I edited; see User:Hillman/Archive. I emphatically do not vouch for anything you might see in more recent versions, although I hope for the best. Unfortunately, general relativity attracts many cranks and the Kerr solution is well known to some of them, so it is likely that at least some future versions of this article will contain slanted information, misinformation, or disinformation. Beware also of external links to outside websites, which may portray a wide variety of pseudoscience or fringe science topics as more respectable than they really are.
Good luck to all students in your search for information, regardless!---CH 01:26, 1 July 2006 (UTC)
