CatDat

Implication Details

Claim: A category has equalizers and is regular-subobject-trivial if and only if it is thin.

Proof: For the forward direction, if f,g:XYf,g : X \rightrightarrows Y are morphisms, their equalizer is a regular monomorphism EXE \hookrightarrow X, hence an isomorphism. But this means f=gf = g. The reverse implication is trivial.

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