Pure Colloquium Seminar - Cornelia Busch (ETHZ) Seminar

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If a group $G$ of finite virtual cohomological dimension has $p$-periodic Farrell cohomology, then the Yagita invariant of this group equals its $p$-period. The group of symplectic $2(p+1)\/\times\/2(p+1)$ matrices over $\Z$ has elementary abelian $p$-subgroups of rank at least $2$ and hence $\SP(2(p+1),\Z)$ and $\SP(2(p+1),\Q)$ do not have $p$-periodic Farrell cohomology. We compute the Yagita invariants of these groups for any odd prime $p$.