Structure

Implication details

Claim: If a category has disjoint finite coproducts and is regular-quotient-trivial, then it is trivial.

Proof: For any object XX, the coequalizer of the two coprojections X⇉X⊔XX \rightrightarrows X \sqcup X is the codiagonal ∇:X⊔X→X\nabla : X \sqcup X \to X. Therefore, these two coprojections are equal. But their equalizer is also the unique morphism !:0→X! : 0 \to X. It follows that !:0→X! : 0 \to X is an isomorphism.

This implication has a dual.

Show 35 categories using this implication