The conjectural induction rule for big partitions with two conormal nodes

Let λ~\tilde\lambda be the regularization of a big partition u u of nn having height HH, and let λˉ1\bar\lambda_1 and h(λ)\overline{h(\lambda)} denote the relevant residues. Let αZp\alpha\in\mathbb Z_p satisfy λ1=h(λ)=α\overline{\lambda_1}=-\overline{h(\lambda)}=\alpha not holding. Suppose that λ~\tilde\lambda has more than one conormal node of residue α\alpha, and let AA and BB be those nodes, with AA above BB. Write Hε\mathcal H_\varepsilon for the partition operation indexed by the displayed sequence ε\varepsilon.

Induction branching conjecture. There are exactly two such conormal nodes, and

[IndαDλ~]={2[Dλ~A]+[Dλ~B],h2,1(λ)p1,2[Dλ~A]+[Dλ~B]+[DH(2,2)(λ~A)],h2,1(λ)=p1 and H=2,2[Dλ~A]+[Dλ~B]+[DH(0,1,1)(λ~A)]+[DH(1,1,0)(λ~A)],h2,1(λ)=p1 and H=3,2[Dλ~A]+[Dλ~B]+[DH(0,1,0H3,1)(λ~A)]+[DH(0,1,0H4,1,0)(λ~A)],h2,1(λ)=p1 and H>3.[\operatorname{Ind}^\alpha D^{\tilde\lambda}]= \begin{cases} 2[D^{\tilde\lambda^A}]+[D^{\tilde\lambda^B}],&h_{2,1}(\lambda)\ne p-1,\\ 2[D^{\tilde\lambda^A}]+[D^{\tilde\lambda^B}]+[D^{\mathcal H_{(-2,2)}(\tilde\lambda^A)}],&h_{2,1}(\lambda)=p-1\text{ and }H=2,\\ 2[D^{\tilde\lambda^A}]+[D^{\tilde\lambda^B}]+[D^{\mathcal H_{(0,-1,1)}(\tilde\lambda^A)}]+[D^{\mathcal H_{(1,-1,0)}(\tilde\lambda^A)}],&h_{2,1}(\lambda)=p-1\text{ and }H=3,\\ 2[D^{\tilde\lambda^A}]+[D^{\tilde\lambda^B}]+[D^{\mathcal H_{(0,-1,0^{H-3},1)}(\tilde\lambda^A)}]+[D^{\mathcal H_{(0,-1,0^{H-4},1,0)}(\tilde\lambda^A)}],&h_{2,1}(\lambda)=p-1\text{ and }H>3. \end{cases}

The bracketed terms denote composition-factor multiplicities.

The conjecture is based on the upper estimates and calculations in known decomposition matrices. The supplied parser marks it as disproved, so it is recorded as refuted despite the conjectural wording in the paper.

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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