Dear category theorists, I have a question concerning the paper "On Closed Categories of Functors" from Brian Day (By the way, this is an excellent paper). Let V be a symmetric monoidal closed category and C a small V-category. The (ordinary) category [C,V] of V-functors admits the sturcure of a V-category in a canonical way. A symmetric monoidal V-category is the enriched analogue of a symmetric-monoidal structure on an ordinary category, i.e. all the structure morphisms are V-morphisms and the coherence conditions are fullfilled. The underlaying category of a symmetric monoidal V-category admits the structure of an ordinary symmetric monoidal category. Brian Day constructs a symmetric monoidal closed structure ([C,V],@,E) on the V-category of V-functors [C,V] for some cases [3.3, 3.6], e.g. if (C,*,e) is a symmetric monoidal V-category [4.1]. The underlaying *category* [C,V] of V-functors admits a closed symmetric monoidal structure from the enriched one by taking the underlaying functor of each V-functor, the underlaying natural transformation of each V-natural transformation. Because a closed symmetric monoidal category is canonically enriched over itself, the category [C,V] gets a [C,V] enrichment in this way. My question is: What does this [C,V]-enrichment of [C,V] have to do with the V-enrichment of [C,V]? Suppose C have a terminal object t. One gets a evaluation functor Ev_t:[C,V]-CAT-->V-CAT. Is this the connection between the two enrichments? Thank you in advance for any help. Tony
Let V be a symmetric monoidal closed category and C a small V-category. Brian Day constructs a symmetric monoidal closed structure ([C,V],@,E) on the V-category of V-functors [C,V] for some cases [3.3, 3.6], e.g. if (C,*,e) is a symmetric monoidal V-category [4.1]. The underlying *category* [C,V] of V-functors admits a closed symmetric monoidal structure from the enriched one by taking the underlying functor of each V-functor, the underlying natural transformation of each V-natural transformation.
Because a closed symmetric monoidal category is canonically enriched over itself, the category [C,V] gets a [C,V] enrichment in this way.
My question is: What does this [C,V]-enrichment of [C,V] have to do with the V-enrichment of [C,V]? Suppose C have a terminal object t. One gets a evaluation functor Ev_t:[C,V]-CAT-->V-CAT. Is this the connection between the two enrichments?
I think what you want here is the following observation. Every closed monoidal V-category E is also an E-category. The unit object j for tensor in E is a monoid and so E(j,-) : E --> V is a monoidal V-functor. Therefore by applying it on hom objects, it induces a 2-functor E-Cat --> V-Cat. In particular, you can apply the 2-functor to E itself to see it as a V-category. Your example is for E = [C,V]. Ross PS I have ordinary- (not enriched-) mailed your message to Brian himself. He may want to add something when he gets it. But I hope I have the story you need!
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street@ics.mq.edu.au -
Tony Meman