The cohomology of semi-simple Lie groups, viewed from infinity

The cohomological restriction map and FP-infinity groups

We ask, following Bartholdi, whether it is true that the kernel of the restriction map from the cohomology of a group G to the cohomology of a finite index subgroup H is finitely generated as an ideal. We show that in case the group has virtual finite cohomological dimension it is true, and we will show that if G does not have virtual finite cohomological dimension it might not be true, even in case G is an FP infinity group.

Dimensions of l^p-cohomology groups

Let G be an infinite discrete group of type FP-infinity and let p>1 be a real number. We prove that the l^p-homology and cohomology groups of G are either 0 or infinite dimensional. We also show that the cardinality of the p-harmonic boundary of a finitely generated group is either 0, 1, or infinity.

The nilpotent filtration and the action of automorphisms on the cohomology of finite p--groups

We study H^*(P), the mod p cohomology of a finite p--group P, viewed as an Out(P)--module. In particular, we study the conjecture, first considered by Martino and Priddy, that, if e_S in Z/p[Out(P)] is a primitive idempotent associated to an irreducible Z/p[Out(P)]--module S, then the Krull dimension of e_SH^*(P) equals the rank of P. The rank is an upper bound by Quillen's work, and the conjecture can be viewed as the statement that every irreducible Z/p[Out(P)]--module occurs as a composition factor in H^*(P) with similar frequency. In summary, our results are as follows. A strong form of th…

Characterization of pseudo-collarable manifolds with boundary

In this paper we obtain a complete characterization of pseudo-collarable $n$-manifolds for $n\geq 6$. This extends earlier work by Guilbault and Tinsley to allow for manifolds with noncompact boundary. In the same way that their work can be viewed as an extension of Siebenmann's dissertation that can be applied to manifolds with non-stable fundamental group at infinity, our main theorem can also be viewed as an extension of the recent Gu-Guilbault characterization of completable $n$-manifolds in a manner that is applicable to manifolds whose fundamental group at infinity is not peripherally st…

辛群、映射类群与有界上同调的稳定性

Symplectic Groups, Mapping Class Groups and the Stability of Bounded Cohomology

本研究探讨映射类群与辛群的有界上同调稳定性，证明映射类群有界上同调不稳定、Mumford-Morita-Miller类稳定多项式无界，辛群2次有界上同调非等距稳定并给出相关范数计算与估计。

Dyer-Lashof operations on Tate cohomology of finite groups

Let k be the field with p>0 elements, and let G be a finite group. By exhibiting an E-infinity-operad action on Hom(P,k) for a complete projective resolution P of the trivial kG-module k, we obtain power operations of Dyer-Lashof type on Tate cohomology H*(G; k). Our operations agree with the usual Steenrod operations on ordinary cohomology. We show that they are compatible (in a suitable sense) with products of groups, and (in certain cases) with the Evens norm map. These theorems provide tools for explicit computations of the operations for small groups G. We also show that the operations in…