The conjecture for categories associated with the subregular nilpotent in G2G_2

Let l7l\geq 7 be an integer not divisible by 33, and let qq be the parameter defining the braided finite tensor category C(G2,G2(a1),l,q)\mathcal{C}(G_2,G_2(a_1),l,q). Write T(ω1)T(\omega_1) and T(ω2)T(\omega_2) for the tilting modules of highest weights ω1\omega_1 and ω2\omega_2, and let [r]l[r]_l denote the quantum integer. The conjecture for C(G2,G2(a1),l,q)\mathcal{C}(G_2,G_2(a_1),l,q).

(1) The Frobenius–Perron dimensions satisfy

FPdim(C(G2,G2(a1),l,q))=6l4(2sin(π/l))8(2sin(2π/l))2,\operatorname{FPdim}(\mathcal{C}(G_2,G_2(a_1),l,q))=6\frac{l^4}{(2\sin(\pi/l))^8(2\sin(2\pi/l))^2},

and

FPdim(T(ω1))=2[3]l+1,FPdim(T(ω2))=[5]l+3[3]l.\operatorname{FPdim}(T(\omega_1))=2[3]_l+1,\qquad \operatorname{FPdim}(T(\omega_2))=[5]_l+3[3]_l.

(2) The category C(G2,G2(a1),l,q)\mathcal{C}(G_2,G_2(a_1),l,q) has the stable Chevalley property.

(3) Its Müger center is equivalent to Rep(S3)\operatorname{Rep}(S_3). The projective covers of the simple objects from Rep(S3)\operatorname{Rep}(S_3) lie in the principal block, and the highest weights of the corresponding tilting modules lie in the alcoves C0C_0, C4C_4, and C7C_7. The formulas have been checked for l=7,11l=7,11 and are compatible with the separately described l=5l=5 semisimplification; the general case remains conjectural.

Sources & referencesView supporting material

Primary source

Victor Ostrik and Alexandra Utiralova, “A non-semisimple Witt class”, arXiv:2602.10519 (2026).

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