Wydawnictwa / Czasopisma IMPAN / Fundamenta Mathematicae / Wszystkie zeszyty

Streszczenie

Let $p$ be a prime, and let ${\cal F}$ be the category of functors from the finite $\Bbb F_p$-vector spaces to all $\Bbb F_p$-vector spaces. The object $\rm Id$ of ${\cal F}$ is the inclusion functor. Let $F$ and $G$ be two objects in ${\cal F}$. If $F$ and $G$ satisfy suitable conditions, the main result of this paper allows one to compute $\mathop{{\rm Ext}}_{\cal F}^*(\mathop{{\rm Id}},G \circ F)$ from the knowledge of $\mathop{{\rm Ext}}_{\cal F}^*(\mathop{{\rm Id}},F)$ and $\mathop{{\rm Ext}}_{\cal F}^*(\mathop{{\rm Id}},G)$.