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Homotopy and homology of p-subgroup complexes


Das, Kaustuv Mukul (1994) Homotopy and homology of p-subgroup complexes. Dissertation (Ph.D.), California Institute of Technology.


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In this thesis we analyzed the simple connectivity of the Quillen complex at [...] for the classical groups of Lie type. In light of the Solomon-Tits theorem, we focused on the case where [...] is not the characteristic prime. Given (p,q) = 1. let dp(q) be the order of [...] in [...]. In this thesis we proved the following result:

Main Theorem. When (p,q) = 1 we have the following results about the simple connectivity of the Quillen complex at p, Ap(G), for the classical groups of Lie type:

1. If G = GLn(q), dp(q) > 2 and mp(G) > 2, then Ap[...](G) is simply connected.

2. If G = [...], then: (a) Ap(G) is Cohen-Macaulay of dimension n - 1 if dp(q) = 1. (b) If nip(G) > 2 and dp(q) is odd, then Ap(G) is simply connected.

3. If G = [...], then: (a) Ap(G) is Cohen-IVlacaulay of dimension n - 1 if [...] and dp(q) = 1. (b) If mp(G) > 2 and dp(q) is odd, then ,Ap(G) is simply connected. (c) If n [...] 3, q [...] 5 is odd, and dp(q) = 2, then Ap(G)(> Z) is simply connected, where Z is the central subgroup of G of order p.

In the course of analyzing the [...]-subgroup complexes we developed new tools for studying relations between various simplicial complexes and generated results about the join of complexes and the [...]-subgroup complexes of products of groups. For example we proved: Theorem A. Let [...] be a map of posets satisfying:

(1) [...] is strict; that is,[...] (2)[...] (3) [...]connected for all [...] with [...].

Then Y n-connected implies X is n-connected.

Theorem A provides us with a tool for studying [...] in terms of [...]. For example, we used this method to prove:

Theorem 8.6. Let G = [...] where [...] is solvable and S is a p-group of symplectic type. Then [...]spherical.

In this thesis we also generated a library of results about geometric complexes which do not arise as [...]-subgroup complexes. This library includes, but is not restricted to, the following:

(l.) the poset of proper nondegenerate subspaces of a 2[...]-dimensional symplectic space -ordered by inclusion - is Cohen-Macaulay of dimension n-2. (2) If q is an odd prime power anal n [...] (with n [...] 5 if q = 3), then the poset of proper nondegenerate subspaces of an n-dimensional unitary space over Fq2 is simply connected.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Mathematics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Aschbacher, Michael
Thesis Committee:
  • Aschbacher, Michael (chair)
  • Wales, David B.
  • Wilson, Richard M.
  • Guralnick, Robert M.
  • Shahriari, Shahriar
Defense Date:12 April 1994
Record Number:CaltechETD:etd-06032004-143153
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2418
Deposited By: Imported from ETD-db
Deposited On:04 Jun 2004
Last Modified:26 Dec 2012 02:51

Thesis Files

PDF (Das_km_1994.pdf) - Final Version
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