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Ends and Coends - Analoguescoends – analogues for higher arity - Horn Filling

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Gerrit Begher
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Consider the setting of categories enriched over a suitable monoidal category V$\mathbb V$.

We define Dist(X,Y):=V−Cat(Xop⊗Y,V).$$\mathrm{Dist}(X,Y):=\mathbb V−\mathrm{Cat}(X^ \mathrm{op}⊗Y,\mathbb V).$$

Recall the definition of ends. Taking the end is an operation of signature

Dist(X,X)→V.$$\mathrm{Dist}(X,X)→\mathbb V.$$

QUESTION: Is there an analogue for functors into V of higher arity. More explicitly: Is there a canonical operation of signature

V−Cat(X?⊗X?⊗X?,V)→V$$\mathbb V−\mathrm{Cat}(X^?⊗X^?⊗X^?,V)→\mathbb V$$

where the ? are to be replaced by either op or nothing.

MOTIVATION: I like to think of the composition $\otimes$ of (2-ary)distributors and the right adjoints to D⊗−$D\otimes−$ and −⊗E$−\otimes E$ as "horn-filling" (in the sense of viewing categories as simplicial sets).

I hope to find a similar situation for "3-ary distributors" - Whenever there is a (oriented?) tetrahedron of 3-ary functors with one side missing we should be able to find the missing side.

So given

U∈Dist3(X,Y,A)$$U\in\mathrm{Dist}^3(X,Y,A)$$ V∈Dist3(Y,Z,A)$$V\in\mathrm{Dist}^3(Y,Z,A)$$ W∈Dist3(Z,X,A)$$W\in\mathrm{Dist}^3(Z,X,A)$$

there should be ?(U,V,W)∈Dist3(X,Y,Z)$$?(U,V,W)\in\mathrm{Dist}^3(X,Y,Z)$$

and related adjoints.

Of course Dist3$\mathrm{Dist}^3$ remains to be defined.

Consider the setting of categories enriched over a suitable monoidal category V.

We define Dist(X,Y):=V−Cat(Xop⊗Y,V).

Recall the definition of ends. Taking the end is an operation of signature

Dist(X,X)→V.

QUESTION: Is there an analogue for functors into V of higher arity. More explicitly: Is there a canonical operation of signature

V−Cat(X?⊗X?⊗X?,V)→V

where the ? are to be replaced by either op or nothing.

MOTIVATION: I like to think of the composition of (2-ary)distributors and the right adjoints to D⊗− and −⊗E as "horn-filling" (in the sense of viewing categories as simplicial sets).

I hope to find a similar situation for "3-ary distributors" - Whenever there is a (oriented?) tetrahedron of 3-ary functors with one side missing we should be able to find the missing side.

So given

U∈Dist3(X,Y,A) V∈Dist3(Y,Z,A) W∈Dist3(Z,X,A)

there should be ?(U,V,W)∈Dist3(X,Y,Z)

and related adjoints.

Of course Dist3 remains to be defined.

Consider the setting of categories enriched over a suitable monoidal category $\mathbb V$.

We define $$\mathrm{Dist}(X,Y):=\mathbb V−\mathrm{Cat}(X^ \mathrm{op}⊗Y,\mathbb V).$$

Recall the definition of ends. Taking the end is an operation of signature

$$\mathrm{Dist}(X,X)→\mathbb V.$$

QUESTION: Is there an analogue for functors into V of higher arity. More explicitly: Is there a canonical operation of signature

$$\mathbb V−\mathrm{Cat}(X^?⊗X^?⊗X^?,V)→\mathbb V$$

where the ? are to be replaced by either op or nothing.

MOTIVATION: I like to think of the composition $\otimes$ of (2-ary)distributors and the right adjoints to $D\otimes−$ and $−\otimes E$ as "horn-filling" (in the sense of viewing categories as simplicial sets).

I hope to find a similar situation for "3-ary distributors" - Whenever there is a (oriented?) tetrahedron of 3-ary functors with one side missing we should be able to find the missing side.

So given

$$U\in\mathrm{Dist}^3(X,Y,A)$$ $$V\in\mathrm{Dist}^3(Y,Z,A)$$ $$W\in\mathrm{Dist}^3(Z,X,A)$$

there should be $$?(U,V,W)\in\mathrm{Dist}^3(X,Y,Z)$$

and related adjoints.

Of course $\mathrm{Dist}^3$ remains to be defined.

Modified: Title
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Gerrit Begher
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Gerrit Begher
  • 3.2k
  • 1
  • 24
  • 33
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