English

When is Group Cohomology Finitary?

Group Theory 2008-03-19 v1 K-Theory and Homology

Abstract

If GG is a group, then we say that the functor Hn(G,)H^n(G,-) is finitary if it commutes with all filtered colimit systems of coefficient modules. We investigate groups with cohomology almost everywhere finitary; that is, groups with nnth cohomology functors finitary for all sufficiently large nn. We establish sufficient conditions for a group GG possessing a finite dimensional model for e.g.e.g. to have cohomology almost everywhere finitary. We also prove a stronger result for the subclass of groups of finite virtual cohomological dimension, and use this to answer a question of Leary and Nucinkis. Finally, we show that if GG is a locally (polycyclic-by-finite) group, then GG has cohomology almost everywhere finitary if and only if GG has finite virtual cohomological dimension and the normalizer of every non-trivial finite subgroup of GG is finitely generated.

Keywords

Cite

@article{arxiv.0803.2540,
  title  = {When is Group Cohomology Finitary?},
  author = {Martin Hamilton},
  journal= {arXiv preprint arXiv:0803.2540},
  year   = {2008}
}

Comments

26 pages

R2 v1 2026-06-21T10:22:16.985Z