The Mod-2 Cohomology of the Bianchi Groups
نویسنده
چکیده
The Bianchi groups are a family of discrete subgroups of PSL2(C) which have group theoretic descriptions as amalgamated products and HNN extensions. Using Bass-Serre theory, we show how the cohomology of these two constructions relates to the cohomology of their pieces. We then apply these results to calculate the mod-2 cohomology ring for various Bianchi groups.
منابع مشابه
A note on the new basis in the mod 2 Steenrod algebra
The Mod $2$ Steenrod algebra is a Hopf algebra that consists of the primary cohomology operations, denoted by $Sq^n$, between the cohomology groups with $mathbb{Z}_2$ coefficients of any topological space. Regarding to its vector space structure over $mathbb{Z}_2$, it has many base systems and some of the base systems can also be restricted to its sub algebras. On the contrary, in ...
متن کاملRing structures of mod p equivariant cohomology rings and ring homomorphisms between them
In this paper, we consider a class of connected oriented (with respect to Z/p) closed G-manifolds with a non-empty finite fixed point set, each of which is G-equivariantly formal, where G = Z/p and p is an odd prime. Using localization theorem and equivariant index, we give an explicit description of the mod p equivariant cohomology ring of such a G-manifold in terms of algebra. This makes ...
متن کاملWeight Reduction for Mod l Bianchi Modular Forms
LetK be an imaginary quadratic field with class number one. We prove that mod l, a system of Hecke eigenvalues occurring in the first cohomology group of some congruence subgroup Γ of SL2(ØK) can be realized, up to twist, in the first cohomology with trivial coefficients after increasing the level of Γ by (l). 1. Motivation and Summary Let G be a connected semisimple algebraic group defined ove...
متن کاملGroup cohomology and control of p–fusion
We show that if an inclusion of finite groups H ≤ G of index prime to p induces a homeomorphism of mod p cohomology varieties, or equivalently an F–isomorphism in mod p cohomology, then H controls p–fusion in G, if p is odd. This generalizes classical results of Quillen who proved this when H is a Sylow p–subgroup, and furthermore implies a hitherto difficult result of Mislin about cohomology i...
متن کاملThe Cohomology of the Sylow 2-subgroup of the Higman-sims Group
Recently there has been substantial progress towards computing the mod 2 cohomology of low rank sporadic simple groups. In fact the mod 2 cohomology of every sporadic simple group not containing (Z/2) has been computed, with the notable exceptions of HS (the Higman–Sims group) and Co3 (one of the Conway groups). The reason for these exceptions is that these two groups have large and complicated...
متن کامل