Conjectural radical presentations of fusion ideals for types B and D

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Let Iℓ(g)I_{\ell}(\mathfrak{g}) be the fusion ideal in the representation ring of the simple Lie algebra g\mathfrak{g}, let I\sqrt{I} denote the radical of an ideal II, and let hˇ(g)\check{h}(\mathfrak{g}) be the dual Coxeter number. For type BrB_r with r≥3r\geq 3, use the fundamental weight ω1\omega_1; for type DrD_r with r≥4r\geq 4, use the fundamental weight ωd\omega_d of minimum Dynkin index.

Conjectural radical presentation. For g\mathfrak{g} of type BrB_r with r≥3r\geq 3,

⟨χ(ℓ+1)ω1,χ(ℓ+2)ω1,…,χ(ℓ+hˇ(g)−1)ω1⟩=⟨χ(ℓ+1)ω1,χ(ℓ+2)ω1,…,χ(ℓ+hˇ(g)−1)ω1,χℓω1+ωr⟩.\sqrt{\langle \chi_{(\ell+1)\omega_1},\chi_{(\ell+2)\omega_1},\ldots,\chi_{(\ell+\check{h}(\mathfrak{g})-1)\omega_1}\rangle}=\langle \chi_{(\ell+1)\omega_1},\chi_{(\ell+2)\omega_1},\ldots,\chi_{(\ell+\check{h}(\mathfrak{g})-1)\omega_1},\chi_{\ell\omega_1+\omega_r}\rangle.

For g\mathfrak{g} of type DrD_r with r≥4r\geq 4,

⟨χ(ℓ+1)ωd,χ(ℓ+2)ωd,…,χ(ℓ+hˇ(g)−1)ωd⟩=⟨χ(ℓ+1)ωd,χ(ℓ+2)ωd,…,χ(ℓ+hˇ(g)−1)ωd,χℓω1+ωr−1,χℓω1+ωr⟩.\sqrt{\langle \chi_{(\ell+1)\omega_d},\chi_{(\ell+2)\omega_d},\ldots,\chi_{(\ell+\check{h}(\mathfrak{g})-1)\omega_d}\rangle}=\langle \chi_{(\ell+1)\omega_d},\chi_{(\ell+2)\omega_d},\ldots,\chi_{(\ell+\check{h}(\mathfrak{g})-1)\omega_d},\chi_{\ell\omega_1+\omega_{r-1}},\chi_{\ell\omega_1+\omega_r}\rangle.

These conjectures refine the theorem's radical inclusions by proposing explicit generators for the corresponding fusion ideals. The preceding text notes that the inclusions in parts (a) and (b) are equalities for types BrB_r, DrD_r, and G2G_2; the additional equalities for types BrB_r and DrD_r remain conjectural.

References

Primary source

Arzu Boysal and Shrawan Kumar, “A conjectural presentation of fusion algebras”, arXiv:0802.3035 (2008).

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