A strong monomorphism in a category is a monomorphism which is right orthogonal to any epimorphism. The dual notion is, of course, strong epimorphism.
If has coequalizers, then any morphism which is right orthogonal to epimorphisms must automatically be a monomorphism.
If has kernel pairs and coequalizers of kernel pairs, then any morphism which is right orthogonal to epimorphisms must automatically be a monomorphism.
Every regular monomorphism is strong. The converse is true if is co-regular.
Every strong monomorphism is extremal; the converse is true if has pushouts.
A nice example of strong monomorphisms in a category are the subspace inclusions in the category of diffeological spaces. In this setting, any subset of a diffeological space is again a diffeological space. If smooth, the inclusion is always a monomorphism, but it is a strong monomorphism if and only if has “enough” plots, that is if is a plot if and only if the composite is a plot.
Let be the category whose objects are the integers , and whose morphisms are generated from arrows
subject to the relations
Then the only epimorphisms and monomorphisms in are the identities, thus every map is right orthogonal to all epimorphisms but only the identities are strong monomorphisms.
pushout of strong monomorphism in quasitopos
Suppose that is either
Suppose that
is a commutative diagram in such that
Then
See at quasitopos this lemma. Note that the result for quasitoposes immediately implies the result for toposes, since all monomorphisms in a topos are regular ( being the equalizer of the arrows in
where is the classifying map of ) and therefore strong.
Last revised on August 27, 2019 at 01:24:59. See the history of this page for a list of all contributions to it.