The conjectural restriction rule for completely splittable partitions

Let λ\lambda be a completely splittable partition of height HH with χ(λ)=p\chi(\lambda)=p, and let αZp\alpha\in\mathbb Z_p. Let AA be the top λ\lambda-addable node, namely the node in the first row. Suppose that λA\lambda^A has more than one normal node of residue α\alpha, and let BB be the bottom λ\lambda-removable node. Let x=[h2,1(λ)p]x=[h_{2,1}(\lambda)\geqslant p] be the indicator of the stated inequality.

Restriction branching conjecture. Except for AA, the only λA\lambda^A-normal node of residue α\alpha is BB, and

[ResαDλA]={2[Dλ~]+[Dλ]+[DH(1,0H3,1,0)(λ)]+x[DH(0,1,0H3,1)(λ)],H>2,2[Dλ~]+[Dλ]+x[DH(1,1)(λ)],H=2.[\operatorname{Res}_\alpha D^{\lambda^A}]= \begin{cases} 2[D^{\tilde\lambda}]+[D^\lambda]+[D^{\mathcal H_{(-1,0^{H-3},1,0)}(\lambda)}]+x[D^{\mathcal H_{(0,-1,0^{H-3},1)}(\lambda)}],&H>2,\\ 2[D^{\tilde\lambda}]+[D^\lambda]+x[D^{\mathcal H_{(1,-1)}(\lambda)}],&H=2. \end{cases}

This is a proposed restriction-side branching formula, based on upper estimates and known decomposition matrices. The source supplies no proof or resolution status.

Sources & referencesView supporting material

Primary source

Vladimir Shchigolev, “On extensions and branching rules for modules close to completely splittable”, arXiv:math/0408164 (2004).

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