Surjectivity conjecture for the weakly integral Witt group

Let W\mathcal{W} be the Witt group of non-degenerate braided fusion categories, let sWs\mathcal{W} be the corresponding group of slightly degenerate braided fusion categories, and let WQ\mathcal{W}_{\mathbb{Q}} and sWQs\mathcal{W}_{\mathbb{Q}} denote their weakly integral Witt subgroups. Let S:WsWS:\mathcal{W}\to s\mathcal{W} be the group homomorphism whose kernel is WIsingZ/16Z\mathcal{W}_{Ising}\cong\mathbb{Z}/16\mathbb{Z}. Weakly integral Witt-group conjecture. The restriction

SWQ:WQsWQ\left.S\right|_{\mathcal{W}_{\mathbb{Q}}}:\mathcal{W}_{\mathbb{Q}}\to s\mathcal{W}_{\mathbb{Q}}

is surjective, equivalently,

WQsWQ×WIsing.\mathcal{W}_{\mathbb{Q}}\cong s\mathcal{W}_{\mathbb{Q}}\times\mathcal{W}_{Ising}.

This is the weakly integral truncation of the question of whether SS is surjective, which is related to the minimal modular extension conjecture for slightly degenerate braided fusion categories. The source states that the general surjectivity question is unresolved, and proposes surjectivity on weakly integral Witt classes.

Sources & referencesView supporting material

Primary source

Terry Gannon and Andrew Schopieray, “Algebraic number fields generated by Frobenius-Perron dimensions in fusion rings”, arXiv:1912.12260 (2019).

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