Talk:Anderson orthogonality theorem

I am sorry, but the article is not very precise and especially the last sentence is incomprehensible (even on a grammatical level):
 * The ground state when for the system when V(r) = 0 and V(r) \neq 0 are orthogonal.

As for the rest of the article, it is not the author's fault that the notion of a magnetic impurity does not seem to have been explained elsewhere on Wikipedia yet, but it would be nice to say something more about it here, since it is necessary to understand this article. Regards, High on a tree 12:04, 20 July 2007 (UTC)
 * Exactly which ground state/ground states of which system are we talking about here?
 * Orthogonal in which sense (in which Hilbert space)?