Höhn's coinvariant Leech lattice conjecture for semisimple cases

Let Λ\Lambda be the Leech lattice, let O(Λ)O(\Lambda) be its isometry group, and let Λg\Lambda_g denote the sublattice orthogonal to the fixed-point sublattice of gO(Λ)g\in O(\Lambda). For a semisimple case in Schellekens' list, let LgL_\mathfrak{g} be the associated even lattice and write R(VΛgg^)R(V_{\Lambda_g}^{\hat{g}}) and R(VLg)R(V_{L_\mathfrak{g}}) for the sets of irreducible modules, equipped with their quadratic forms qq given by conformal weight modulo Z\mathbb{Z}. Höhn's conjecture. For each semisimple case in Schellekens' list, there exists an isometry gO(Λ)g\in O(\Lambda) such that

(R(VΛgg^),q)(R(VLg),q)(R(V_{\Lambda_g}^{\hat{g}}),q)\cong (R(V_{L_\mathfrak{g}}),-q)

as quadratic spaces. This conjecture proposes that the fusion quadratic space of the orbifold associated with a suitable coinvariant Leech lattice realizes the quadratic space required by the corresponding semisimple case; the source presents it as a proposal, and no resolution is supplied here.

Sources & referencesView supporting material

Primary source

Ching Hung Lam, “Cyclic orbifolds of lattice vertex operator algebras having group like fusions”, arXiv:1805.10778 (2019).

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