Abstract
LetG be a profinite group which has an open subgroupH such that the cohomologicalp-dimensiond≔cdp(H) is finite (p is a fixed prime). The main result of this paper expresses thep-primary part of high degree cohomology ofG in terms of the elementary abelianp-subgroups ofG: From the latter one constructs a natural profinite simplicial setA G, on whichG acts by conjugation. ThenH n(G,M)≅H nG (AG,M) holds forn≧d+r and everyp-primary discreteG-moduleM (r≔p-rank ofG). If one uses profinite Farrell cohomology, which is introduced in this paper, the analogous fact holds in all degrees. These results are the profinite analogues of theorems by K.S. Brown for discrete groups.
Similar content being viewed by others
References
[Bn] D. J. Benson: Representations and Cohomology. (2 volumes) Cambridge Univ. Press, Cambridge, 1991
[Br1] K.S. Brown: Groups of virtually finite dimension. In: Homological Group Theory, ed. C.T.C. Wall, London Math. Soc. Lect. Notes36, Cambridge, 1979, pp. 27–70
[Br2] K. S. Brown: Cohomology of Groups. Graduate Texts in Mathematics87, Springer, New York Heidelberg Berlin, 1982
[Bru] A. Brumer: Pseudocompact algebras, profinite groups and class formations. J. Algebra4, 442–470 (1966)
[De] P. Deligne: Théorie de Hodge III. Publ. Math. Inst. Hautes Etudes Scient.44, 5–77 (1974)
[F] F. T. Farrell: An extension of Tate cohomology to a class of infinite groups. J. Pure Applied Algebra10, 153–161 (1977)
[GS] O. Goldman, C.-H. Sah: On a special class of locally compact rings. J. Algebra4, 71–95 (1966)
[G] A. Grothendieck: sur quelques points d'algèbre homologique. Tôhoku Math. J.9, 119–221 (1957)
[EGA] A. Grothendieck: Éléments de Géométrie Algébrique. Chap III, 1ère Partie. Publ. Math. IHES11, Paris, 1961
[Q1] D. Quillen: The spectrum of an equivariant cohomology ring: I. Ann. Math.94, 549–572 (1971)
[Q2] D. Quillen: Homotopy properties of the poset of nontrivialp-subgroups of a group. Adv. Math.28, 101–128 (1978)
[Sch1] C. Scheiderer: Quasi-augmented simplicial spaces, with an application to cohomological dimension. J. Pure Applied Algebra81, 293–311 (1992)
[Sch2] C. Scheiderer: Real and Étale Cohomology. Lect. Notes Math.1588, Springer, Berlin Heidelberg New York, 1994
[S1] J.-P. Serre: Cohomologie Galoisienne. Cinquième édition. Lect. Notes Math.5, Springer, Berlin Heidelberg New York, 1994
[S2] J.-P. Serre: Sur la dimension cohomologique des groupes profinis. Topology3, 413–420 (1965)
[S3] J.-P. Serre: Cohomologie des groupes discrets. Ann. Math. Studies70, 77–169 (1971)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Scheiderer, C. Farrell cohomology and Brown theorems for profinite groups. Manuscripta Math 91, 247–281 (1996). https://doi.org/10.1007/BF02567954
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF02567954