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13 votes

Skeleton of a braided monoidal category

Yes. This follows from two simple facts: If $F:C \simeq D$ is an equivalence of categories, and $D$ has a braided monoidal structure, then there exists a braided monoidal structure on $C$ and an enh …
Chris Schommer-Pries's user avatar
4 votes

Internal Hom of Deligne' tensor product

That equation is not correct. You should be suspicious because the definition of the $\mathcal{C}$-module category structure on $\mathcal{M} \boxtimes \mathcal{N}$ doesn't use the $\mathcal{C}$-module …
Chris Schommer-Pries's user avatar
6 votes
Accepted

A tensor category need not be isomorphic to a strict tensor category

First consider the category $\mathcal{C}_G$ with its bifunctor $\otimes$ and unit. How many ways are there to enhance this to a monoidal category structure? The missing data are precisely the associat …
Chris Schommer-Pries's user avatar
7 votes
Accepted

Categorical models for truncations of the sphere spectrum

I don't understand what you mean about the "directed sphere" so will focus on the other questions. The free Picard $n$-category on one object has a description as a bordism $n$-category. Specifically …
Chris Schommer-Pries's user avatar
23 votes
5 answers
3k views

Do all 3D TQFTs come from Reshetikhin-Turaev?

The Reshetikhin-Turaev construction take as input a Modular Tensor Category (MTC) and spits out a 3D TQFT. I've been told that the other main construction of 3D TQFTs, the Turaev-Viro State sum constr …
Chris Schommer-Pries's user avatar
8 votes
Accepted

What structure on a monoidal category would make its 2-category of module categories monoid...

Here is one set of data that will be sufficient. To get the monoidal structure you don't actually need a (monoidal) functor $C \to C \boxtimes C$. It is sufficient to have a bimodule category M from C …
Chris Schommer-Pries's user avatar
2 votes
Accepted

Braided monoidal category, example

The answer is no in general. Here is a counter example. Let us work over a ground field $k$, and let $ H = \oplus_n k$ be the direct sum of $n$ copies of $k$, with $n \geq 2$. This is a commutative, c …
Chris Schommer-Pries's user avatar
15 votes
2 answers
1k views

Categorifying the Reals via von Neumann Algebras?

So one way to categorify the natural numbers is to replace them with vector spaces. Then the dimension of the vector space reproduces the natural number. More generally you can categorify integers to …
Chris Schommer-Pries's user avatar
4 votes
Accepted

Why is the category of strong braided functors from the braid category to a braided monoidal...

It is indeed true that any strong braided monoidal functor from the braid category to a strict braided monoidal category is equivalent to a strict braided monoidal functor, however that comes out of t …
Chris Schommer-Pries's user avatar
6 votes

When does a monoidal functor between ribbon categories preserve cups and caps, but not neces...

The categories of (finite dimensional) vector spaces and super vector spaces are rigid and symmetric monoidal and so admit ribbon structure where the twist is trivial. The forgetful functor from super …
Chris Schommer-Pries's user avatar