The generic-degree conjecture for decomposition numbers

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Let WW be a complex reflection group. Let θ:q↦ξ\theta:q\mapsto\xi be a specialization of Hq(W){\mathcal H}_q(W), and let (dχ,ϕθ)χ∈Irr⁡(W), ϕ∈Irr⁡(Hξ)(d_{\chi,\phi}^{\theta})_{\chi\in\operatorname{Irr}(W),\,\phi\in\operatorname{Irr}({\mathcal H}_\xi)} be the corresponding decomposition matrix. For each ϕ∈Irr⁡(Hξ)\phi\in\operatorname{Irr}({\mathcal H}_\xi), the generic-degree conjecture asserts that

θ(∑χ∈Irr⁡(W)dχ,ϕθsχ)≠0.\theta\left(\sum_{\chi\in\operatorname{Irr}(W)}\frac{d_{\chi,\phi}^{\theta}}{s_\chi}\right)\neq 0.

Equivalently, using the notation of the source's Lemma GR\mathrm{GR}, ∑χ∈Irr⁡(W)dχ,ϕθDχP\sum_{\chi\in\operatorname{Irr}(W)}d_{\chi,\phi}^{\theta}D_\chi^P has as many factors of the form (q−ξ)(q-\xi) as P(y)P(y). The conjecture was checked in all cases presented in the paper and was proved for type AA and all exceptional Weyl groups, so it is not open in those cases; its general status is not resolved by the supplied text.

References

Primary source

Maria Chlouveraki and Hyohe Miyachi, “Decomposition matrices for d-Harish-Chandra series: the exceptional rank two cases”, arXiv:1008.3413 (2011).

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