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18 votes
2 answers
1k views

Monoidal categories whose tensor has a left adjoint

Is there a name for monoidal categories $(\mathscr V, \otimes, I)$ such that $\otimes$ has a left adjoint $(\ell, r) : \mathscr V \to \mathscr V^2$? Have they been studied anywhere? What are some inte …
varkor's user avatar
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10 votes
0 answers
124 views

V-categories enriched in a monoidal V-category

In an email to the categories mailing list dated 21 August 2003, Street writes: Max reminded me of his old result (not in the LaJolla Proceedings, but known soon after) that a monoidal V-category is …
varkor's user avatar
  • 10.7k
7 votes
Accepted

Enriched categories over a semi-monoidal category

Expanding upon my comment: categories without units are called semicategories. You define a notion of semicategory enriched in a semigroupal category, which is what you describe. The Yoneda lemma is s …
varkor's user avatar
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7 votes
1 answer
337 views

Strictification for closed monoidal categories

The strictification theorem for monoidal categories states that every monoidal categorically is monoidally equivalent to a strict monoidal category. Is there a strictification theorem for closed monoi …
varkor's user avatar
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6 votes
0 answers
99 views

Is the symmetry compatibility condition in Fox's theorem necessary?

Let $(\mathscr V, \otimes, 1, \sigma)$ be a symmetric strict monoidal category whose unit is terminal. Suppose that every object $A$ is equipped with the structure of a cocommutative comonoid $1 \xlef …
varkor's user avatar
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5 votes
1 answer
280 views

3-functoriality of the lax Gray tensor product

In Formal category theory: adjointness for 2-categories, Gray defines a tensor product of 2-categories, now more commonly known as the lax Gray tensor product, which I will denote by $\otimes_l$. For …
varkor's user avatar
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4 votes
Accepted

When is an object determined by the number of maps from the other objects?

The first question is the main topic of two recent papers: Reggio's Polyadic Sets and Homomorphism Counting, which is also a good reference for previous results in the literature (including that of P …
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4 votes

Being (co)cartesian as a property (rather than structure) of a plain monoidal category

I don't have a counterexample to show that (3) is not superfluous, but I can provide some motivation for it. First, let us recall what is probably the most well known characterisation of cartesian mon …
varkor's user avatar
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4 votes
0 answers
95 views

Coherence for closed bicategories

A right-closed bicategory [1] is a bicategory that has all right extensions (i.e. right adjoints to precomposition with a fixed 1-cell). A one-object right-closed bicategory is therefore a right-close …
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4 votes
0 answers
48 views

Bicategories in which the composition functors $\circ_{A, B, C}$ admit right adjoints

In Bénabou's 1967 Introduction to Bicategories, he mentions that, in a forthcoming part II, he would study bicategories $\mathcal K$ in which each composition functor $$\circ_{A, B, C} \colon \mathcal …
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3 votes

Rectifying the definition of a closed category

While relevant references have been mentioned in the comments and in john's answer, I don't believe these fully answer the question as asked, at least without doing a little further reading, so here's …
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3 votes
0 answers
88 views

Reference for the monoidal category structure $X \otimes Y = X + Y + X \times Y$ on a distri...

Given a distributive category $\mathscr C$ (more generally a rig category), we can define a (semicocartesian) monoidal category structure on $\mathscr C$ with tensor product given by $X \otimes Y := X …
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  • 10.7k
3 votes

Strictification for closed monoidal categories

I have not been able to find an explicit reference for this in the literature, so I will sketch a proof here. Steve Lack suggested that one could make use of Mac Lane's proof of strictification for mo …
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2 votes
Accepted

Nomenclature help: action vs. module and “pointed” monadic algebras are module objects?

Action versus module In modern category theory parlance, action and module are typically interchangeable, and their use comes down to author preference: this is a historical artefact of the differing …
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1 vote

Transporting monoidal structure along adjunction

A relevant reference is §3 of Kelly's Doctrinal adjunction: in particular, see Theorem 3.1, which states that, if the adjunction is reflective, then the subcategory inherits monoidal structure if and …
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