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2 votes

Is the category of spherical fusion categories regular? (i.e. is image factorisation possible?)

I think the following is true, and what I was looking for. A tensor functor $F: \mathcal{C} \to \mathcal{D}$ is called dominant (sometimes called "surjective") if for any $Y: \mathcal{D}$, there is a …
Manuel Bärenz's user avatar
2 votes
1 answer
136 views

Is the category of spherical fusion categories regular? (i.e. is image factorisation possible?)

Consider the category where objects are strict spherical fusion categories and morphisms are strict spherical functors (preserving cups and caps). I am wondering whether there is some kind of image fa …
Manuel Bärenz's user avatar
3 votes
1 answer
170 views

Pivotal functors of that are substantially different from finite group homomorphisms

Fusion categories can be seen as generalisations of the representation category of finite groups. I'm interested in spherical fusion categories. I'm trying to find "interesting" functors from a spheri …
Manuel Bärenz's user avatar
1 vote
Accepted

Pivotal functors of that are substantially different from finite group homomorphisms

I've been thinking about this since longer already and just realised a really easy example. I was a bit of a blockhead in thinking that for any inclusion functor $F$, we must have that $F\Omega_\mathc …
Manuel Bärenz's user avatar
4 votes
0 answers
88 views

Are there any dominant pivotal functors such that the regular representation is not mapped o...

This question is related to Pivotal functors of that are substantially different from finite group homomorphisms. A tensor functor $F: \mathcal{C} \to \mathcal{D}$ is called dominant (sometimes calle …
Manuel Bärenz's user avatar
12 votes
1 answer
527 views

Is there a "killing" lemma for G-crossed braided fusion categories?

Edit: I found a serious flaw in the question and my answer, and I had to change a lot. The basic question is still there, but the details are a lot different. Premodular categories In braided spheri …
Manuel Bärenz's user avatar
9 votes
2 answers
399 views

What is a true invariant of $G$-crossed braided fusion categories?

Definition. An invariant of a (spherical) fusion category with extra structure is a number or a set or tuple of numbers preserved under (appropriate) equivalences. (Spherical) fusion categories have …
Manuel Bärenz's user avatar
2 votes
Accepted

Is there a "killing" lemma for G-crossed braided fusion categories?

Edit: I used to believe that there is a possible generalisation stemming from work of Altschüler and Bruguières. (See Appendix C in Drinfeld, Gelaki, Nikshych, Ostrik - On braided fusion categories I) …
Manuel Bärenz's user avatar
5 votes
1 answer
302 views

Is every premodular category the *full* subcategory of a modular category?

In Müger's article "Conformal Field Theory and Doplicher-Roberts Reconstruction", he defines the "modular closure" of a braided monoidal category. So every braided monoidal category (and therefore eve …
Manuel Bärenz's user avatar
5 votes
2 answers
1k views

When is the endofunctor category of a monoidal category braided? When is it ribbon? Fusion? ...

Given a category $\mathcal{C}$, we can define the category of endofunctors $\operatorname{Cat}(\mathcal{C})$, with objects functors $F: \mathcal{C} \to \mathcal{C}$ and morphisms natural transformatio …
Manuel Bärenz's user avatar
9 votes
1 answer
267 views

Is the modularisation of a unitary fusion category always unitary?

Suppose $\mathcal{C}$ is a unitary ribbon fusion category. Also assume that its symmetric centre has trivial twist and trivial pivotal structure, i.e. is tannakian. Thus, the Müger/Bruguières modulari …
Manuel Bärenz's user avatar
2 votes
1 answer
152 views

How nontrivial can "central extensions of ribbon fusion categories" be?

In a sense, this is a follow up on this question, but one PhD programme later. Let $\mathcal{C}$ be ribbon fusion. By $\mathcal{C}'$, we denote the symmetric centre, i.e. the full subcategory of obje …
Manuel Bärenz's user avatar
8 votes
0 answers
679 views

What classifies involutive automorphisms on finite groups? What classifies involutions on fi...

Groups Let $G$ be a finite group. An involutive automorphism on $G$ is an automorphism $i\colon G \to G$ such that $i^2 = 1_G$. Question 1. What classifies involutive automorphisms on a given (non-a …
Manuel Bärenz's user avatar
2 votes
1 answer
152 views

Modularisation on group representations with arbitrary braiding

Applying the modularisation/deequivariantisation procedure to the representation category $\operatorname{Rep}_G$ of a finite group $G$ with trivial braiding gives the fibre functor to vector spaces. W …
Manuel Bärenz's user avatar
6 votes
1 answer
337 views

Is there a quotient or exact sequence of symmetric, premodular (ribbon fusion) and modular c...

In Walker and Wang's article about (3+1)-TQFTs from premodular categories, they say on page 14 that you can take a quotient of a premodular category $\mathcal{C}$ by its symmetric fusion subcategory …
Manuel Bärenz's user avatar

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