Structure

Implication details

Claim: If a category is core-connected and is locally finite, then it is retract-trivial.

Proof: A core-connected locally finite category is equivalent to BMBM for a finite monoid MM. A finite monoid MM satisfies the property xy=1  ⟹  yx=1xy=1 \implies yx=1. In fact, when xy=1xy=1 holds, the map m↦xmm \mapsto xm is surjective, hence injective. Thus, x(yx)=x=x(1)x(yx)=x=x(1) implies yx=1yx=1.
Show 12 categories using this implication