A Brief History of the Positivity Conjecture in Tensor Category

Geoffrey Mason
2019 Bulletin of the Institute of Mathematics Academia Sinica NEW SERIES  
We show the existence of a finite group G having an irreducible character χ with Frobenius-Schur indicator ν2(χ)=+1 such that χ 2 has an irreducible constituent ϕ with ν2(ϕ)=−1. This provides counterexamples to the positivity conjecture in rational CFT and a conjecture of Zhenghan Wang about pivotal fusion categories.
doi:10.21915/bimas.2019202 fatcat:lif3axbexnf7lpidsgbavbgg24