Resumen de Weakly additive cohomology
In this paper the concept of weakly additive cohomology theory is introduced as a variant of the known concept of additive cohomology theory. It is shown that for a closed A in X the singular homology of the pair (X, X-A) (with some fixed cohomology group) regarded as a furcter of A is a weakly additive cohomology theory on any collectionwise normal space X. Furthermore, every compactly supported cohomology theory is weakly additive.
The main result is a comparison theorem for two cohomology theories on X both of which are additive or both of which are weakly additive which recomposes the previously known comparison theorems.
