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Descent in Buildings (Hardcover) (Bernhard Muhlherr & Holger P. Petersson & Richard M. Weiss)
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Descent in Buildings begins with the resolution of a major open question about the local structure of Bruhat-****** buildings. The authors then put their algebraic solution into a geometric context by developing a general fixed point theory for groups acting on buildings of arbitrary type, giving necessary and sufficient conditions for the residues fixed by a group to form a kind of subbuilding or "form" of the original building. At the center of this theory is the notion of a ****** index, a combinatorial version of the notion of an index in the relative theory of algebraic groups. These results are combined at the end to show that every exceptional Bruhat-****** building arises as a form of a "residually pseudo-split" Bruhat-****** building. The book concludes with a display of the ****** indices associated with each of these exceptional forms.
This is the third and final volume of a trilogy that began with Richard Weiss'The Structure of Spherical Buildings and The Structure of Affine Buildings.