2Mon𝒲𝒾𝓀𝒾

Categorical Enrichment

Enrichment is the categorical method of expressing that morphisms of a certain previewcategory come with extra structure. For instance, monotone maps in 𝐏𝐨𝐬𝐞𝐭 can themselves be equipped with a (pointwise) ordering, meaning that for every poset 𝑋 and π‘Œ, 𝐏𝐨𝐬𝐞𝐭(𝑋,π‘Œ) is more than a set, it is a poset.

Strict enrichment

For this section, let 𝒱︀ be a previewmonoidal previewcategory.

Definition Enriched category An 𝒱︀-enriched category π’žοΈ€ is

Objects
a set of objects π’žοΈ€;
Morphisms
for every objects 𝑋,π‘Œ:π’žοΈ€, a 𝒱︀ object π’žοΈ€(𝑋,π‘Œ);
Identity
for every object 𝑋:π’žοΈ€, there is a 𝒱︀ morphism: id𝑋:1β†’π’žοΈ€(𝑋,𝑋)
Composition
for every objects 𝑋,π‘Œ,𝑍:π’žοΈ€, there is a 𝒱︀ morphism ∘:π’žοΈ€(π‘Œ,𝑍)βŠ—π’žοΈ€(𝑋,π‘Œ)β†’π’žοΈ€(𝑋,𝑍)
Associativity

Weak enrichment