8
$\begingroup$

Recently (what I believe are) all multiplicity-free fusion categories up to rank 7 have been posted on the AnyonWiki. Most of the fusion rings belonging to these categories belong to one of the following classes:

  • Finite group rings, e.g., cyclic groups of order $1,\ldots,7$, $D_3$, etc
  • Representation rings of finite groups, e.g., $\text{Rep}(D_3),\text{Rep}(S_4)$, etc
  • Fusion rings related to quantum groups, e.g., $\text{SU}(2)_{k}$ for $k=1,\ldots,6$, $\text{SO}(2N+1)_{2}$ for $N=1,\ldots,3$, etc
  • Fusion rings related to subfactors, e.g., a ring which we called Pseudo $\text{PSU}(2)_6$ (for now)
  • Extensions of the above, such as $\text{HI}(\mathbb{Z}_3)$, $\text{TY}(G)$, for all finite abelian groups $G$ with $|G|<7$
  • Products of the above, e.g. $\mathbb{Z}_2 \times R$ for any fusion ring $R$ with rank $\leq 3$, etc
  • Zestings of the above
  • Adjoint fusion rings of rings related to quantum groups, e.g., $\text{Adj}(\text{SO}(11)_2)$, $\text{Adj}(\text{SO}(16)_2)$

There are a few fusion rings that I don't immediately recognize as any of the above, though. (Which doesn't mean they aren't of the form above)

So, I wondered if anyone recognizes some of the fusion rings below as being related to some known constructions. They are all categorifiable into a unitary fusion category, but none of the categories admit a braided structure.

  1. The Moore-Read fusion ring

This one is known from physics. It has Frobenius-Perron dimensions $(1,1,1,1,\sqrt{2},\sqrt{2})$ and the following multiplication table

$\begin{array}{|llllll|} \hline \mathbf{1} & \mathbf{2} & \mathbf{3} & \mathbf{4} & \mathbf{5} & \mathbf{6} \\ \mathbf{2} & \mathbf{1} & \mathbf{4} & \mathbf{3} & \mathbf{5} & \mathbf{6} \\ \mathbf{3} & \mathbf{4} & \mathbf{2} & \mathbf{1} & \mathbf{6} & \mathbf{5} \\ \mathbf{4} & \mathbf{3} & \mathbf{1} & \mathbf{2} & \mathbf{6} & \mathbf{5} \\ \mathbf{5} & \mathbf{5} & \mathbf{6} & \mathbf{6} & \mathbf{3}+\mathbf{4} & \mathbf{1}+\mathbf{2} \\ \mathbf{6} & \mathbf{6} & \mathbf{5} & \mathbf{5} & \mathbf{1}+\mathbf{2} & \mathbf{3}+\mathbf{4} \\ \hline \end{array}$

Is there any way that this ring fits in the groups above?

  1. A ring we called Pseudo $\text{Rep}(S_4)$

Its multiplication table looks a lot like that from $\text{Rep}(S_4)$. It is listed in this paper at page 11 but the paper also says: Model Unknown. Its Frobenius-Perron dimensions are $(1,1,2,3,3)$ and its multiplication table is the following.

$\begin{array}{|lllll|} \hline \mathbf{1} & \mathbf{2} & \mathbf{3} & \mathbf{4} & \mathbf{5} \\ \mathbf{2} & \mathbf{1} & \mathbf{3} & \mathbf{5} & \mathbf{4} \\ \mathbf{3} & \mathbf{3} & \mathbf{1}+\mathbf{2}+\mathbf{3} & \mathbf{4}+\mathbf{5} & \mathbf{4}+\mathbf{5} \\ \mathbf{4} & \mathbf{5} & \mathbf{4}+\mathbf{5} & \mathbf{2}+\mathbf{3}+\mathbf{4}+\mathbf{5} & \mathbf{1}+\mathbf{3}+\mathbf{4}+\mathbf{5} \\ \mathbf{5} & \mathbf{4} & \mathbf{4}+\mathbf{5} & \mathbf{1}+\mathbf{3}+\mathbf{4}+\mathbf{5} & \mathbf{2}+\mathbf{3}+\mathbf{4}+\mathbf{5} \\ \hline \end{array}$

  1. A ring called $\text{FR}^{7,1,2}_{3}$ of which I have no idea where it comes from. Its Frobenius-Perron dimensions are $(1,1,1,1,2,2,2)$ and it has the following multiplication table

$\begin{array}{|lllllll|} \hline \mathbf{1} & \mathbf{2} & \mathbf{3} & \mathbf{4} & \mathbf{5} & \mathbf{6} & \mathbf{7} \\ \mathbf{2} & \mathbf{1} & \mathbf{4} & \mathbf{3} & \mathbf{5} & \mathbf{6} & \mathbf{7} \\ \mathbf{3} & \mathbf{4} & \mathbf{2} & \mathbf{1} & \mathbf{7} & \mathbf{6} & \mathbf{5} \\ \mathbf{4} & \mathbf{3} & \mathbf{1} & \mathbf{2} & \mathbf{7} & \mathbf{6} & \mathbf{5} \\ \mathbf{5} & \mathbf{5} & \mathbf{7} & \mathbf{7} & \mathbf{1}+\mathbf{2}+\mathbf{6} & \mathbf{5}+\mathbf{7} & \mathbf{3}+\mathbf{4}+\mathbf{6} \\ \mathbf{6} & \mathbf{6} & \mathbf{6} & \mathbf{6} & \mathbf{5}+\mathbf{7} & \mathbf{1}+\mathbf{2}+\mathbf{3}+\mathbf{4} & \mathbf{5}+\mathbf{7} \\ \mathbf{7} & \mathbf{7} & \mathbf{5} & \mathbf{5} & \mathbf{3}+\mathbf{4}+\mathbf{6} & \mathbf{5}+\mathbf{7} & \mathbf{1}+\mathbf{2}+\mathbf{6} \\ \hline \end{array}$

it is related via the testing construction to this ring with the same dimensions but a reshuffle of some of its structure constants.

$\begin{array}{|lllllll|} \hline \mathbf{1} & \mathbf{2} & \mathbf{3} & \mathbf{4} & \mathbf{5} & \mathbf{6} & \mathbf{7} \\ \mathbf{2} & \mathbf{1} & \mathbf{4} & \mathbf{3} & \mathbf{5} & \mathbf{6} & \mathbf{7} \\ \mathbf{3} & \mathbf{4} & \mathbf{2} & \mathbf{1} & \mathbf{5} & \mathbf{7} & \mathbf{6} \\ \mathbf{4} & \mathbf{3} & \mathbf{1} & \mathbf{2} & \mathbf{5} & \mathbf{7} & \mathbf{6} \\ \mathbf{5} & \mathbf{5} & \mathbf{5} & \mathbf{5} & \mathbf{1}+\mathbf{2}+\mathbf{3}+\mathbf{4} & \mathbf{6}+\mathbf{7} & \mathbf{6}+\mathbf{7} \\ \mathbf{6} & \mathbf{6} & \mathbf{7} & \mathbf{7} & \mathbf{6}+\mathbf{7} & \mathbf{3}+\mathbf{4}+\mathbf{5} & \mathbf{1}+\mathbf{2}+\mathbf{5} \\ \mathbf{7} & \mathbf{7} & \mathbf{6} & \mathbf{6} & \mathbf{6}+\mathbf{7} & \mathbf{1}+\mathbf{2}+\mathbf{5} & \mathbf{3}+\mathbf{4}+\mathbf{5} \\ \hline \end{array}$

$\endgroup$

1 Answer 1

4
$\begingroup$

These fusion categories are all weakly integral, each with an FPdim less than 84, and therefore, they are all weakly group-theoretical by this paper. Consequently, they can all be described using models that are, to varying degrees, derived from finite group theory.

The first fusion ring is recognized as N°3 of rank 6 in this paper, and should have a model from zesting.

For the second one, see the last sentence of this comment by Eric Rowell (with $N=3$):

The other fusion rules could potentially be obtained as a Z2-equivariantization of the near-group categories of type Z/N +(N-1) in the Evans-Gannon notation. Just a guess, but the numerology seems to work out.

About the two last ones, what about zestings of $ch(Q_{16})$ and $ch(SD_{16})$?

$\endgroup$
8
  • $\begingroup$ Thanks! That is interesting info! Sadly it also means there is something wrong with my zesting software since I only find orbits with 2 elements when I zest MF fusion rings up to rank 7 and according to the paper all rings of rank 6 with FPDim = 8 should be zestings of each other. :( $\endgroup$
    – Gert
    Commented Feb 24 at 11:26
  • $\begingroup$ @Gert Can you develop a bit your comment. What is MF? $\endgroup$ Commented Feb 24 at 11:34
  • $\begingroup$ Multiplicity-Free. I wrote a little application some time ago that tries all possible ways that a zesting could affect a fusion ring. When I applied it to the multiplicity-free fusion rings up to rank 7 I only find that each ring is related to at most one other ring via zesting. The software was written in a rush so it could very well be that I made a mistake somewhere. I'm in the last week before the PhD. deadline so don't have time for debugging but I'll redo the calculations afterwards. $\endgroup$
    – Gert
    Commented Feb 24 at 12:11
  • $\begingroup$ @Gert I will also review it. It's great that you wrote a code for this purpose. The machine should be significantly more efficient than a human at this type of verification. $\endgroup$ Commented Feb 24 at 12:17
  • $\begingroup$ @Gert Does your code classify the zestings, or the braided zestings? If it's the latter, being much more restrictive than the former, that could be an explanation. $\endgroup$ Commented Feb 24 at 12:52

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .