On the LS-category of homomorphisms of groups with torsion

Abstract

We prove the equality $\cat(\phi)=\cd(\phi)$ for homomorphisms $\phi:\Gamma\to \Lambda$ between finitely generated abelian groups $\Gamma$ and $\Lambda$, where $\phi(T(\Gamma))=0$ for the torsion subgroups $T(\Gamma)$ of $\Gamma$.