On the Simple Connectedness of a Chamber System Associated to a Twin Building

by Bernhard Mühlherr

Abstract:
We prove that the chamber system of opposite chambers in a 2-spherical twin building having no 'small' residues is simply 2-connected. This result provides another approach to the Extension-Theorem for 2-spherical twin buildings and it gives a presentation as an amalgam of certain Kac-Moody groups.

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1991 Mathematics Subject Classification: 51E24 .

Contact: Bernhard.Muehlherr@Mathematik.Uni-Dortmund.DE