Implication Details
Claim: If a category has binary copowers and is left cancellative, then it is thin.
Proof: For every object the codiagonal is a split epimorphism, and by assumption a monomorphism, hence an isomorphism. Hence, the two inclusions coincide. Now, if are two morphisms, consider the induced morphism and compute .
Show 27 categories using this implication
- category of finite sets and bijections
- delooping of a group
- delooping of an infinite countable group
- delooping of a non-trivial finite group
- delooping of an infinite uncountable group
- delooping of the additive monoid of natural numbers
- delooping of the additive monoid of ordinal numbers
- category of finite sets and injections
- category of finite sets
- category of fields
- category of Jónsson-Tarski algebras
- category of M-sets
- category of metric spaces with continuous maps
- category of sets with a distinguished subset
- category of schemes
- category of sets
- category of set functions and commutative squares
- category of countable sets
- category of sets with finite-to-one maps
- category of pairs of sets
- category of sheaves
- category of combinatorial species
- category of Z-functors
- forked commutative square
- category of simplicial sets
- walking fork
- walking parallel pair