Consider the map $$i\colon A\sqcup A\to A$$ where $i=(Id_{A},Id_{A})$. Is this map a cofibration? Actually, I know that isomorphisms are cofibrations and pushouts of cofibrations are cofibrations. But I do not know what tools to use to prove that this map is a cofibration (if it is).
2026-02-23 04:45:27.1771821927
Is this map a cofibration in a model category?
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No, this is false. Consider the standard model structure on simplicial sets. The cofibrations are precisely the monomorphisms in this structure. However, unless $A$ is the empty simplicial set, your $i$ is never a monomorphism.