First Author: Jacques Th\'evenaz
e-mail: Jacques.Thevenaz@ima.unil.ch
Address: Institut de Math\'ematiques,
Universit\'e de Lausanne,
CH--1015 Lausanne,
Switzerland

Second Author: Peter Webb
email: webb@math.umn.edu
Address:
School of Mathematics,
University of Minnesota,
Minneapolis MN 55455

Title:
Homotopy equivalence of posets with a group action

Abstract:
We provide an equivariant version of Quillen's Theorem A, in the case of 
posets. We also prove that the complex of normal chains of non-identity 
p-subgroups is homotopy equivalent to the complex of all chains, and 
provide a reference for the fact that in a finite group of Lie type in 
characteristic p, the subgroups which are the largest normal p-subgroup 
of their normalizer are the unipotent radicals of parabolic subgroups.

This is a preprint version of the paper which appeared in 
J. Combinat. Theory Ser. A. 56 (1991), 173-181.