Conjectural classification of ps-idempotents by unrefined endo-parameters

Let G{\rm G} be a classical group, let ZG,Z[1/p]st\mathfrak{Z}_{{\rm G},\overline{\mathbb{Z}}[1/p]}^{\operatorname{st}} denote the stable center, and let EP(G)\mathcal{EP}({\rm G}) be the set of unrefined endo-parameters for G{\rm G}. A ps-idempotent is a primitive idempotent of this stable center. Ps-idempotent classification conjecture. There is a natural bijection

{primitive idempotents of ZG,Z[1/p]st}EP(G),\left\{\text{primitive idempotents of }\mathfrak{Z}_{{\rm G},\overline{\mathbb{Z}}[1/p]}^{\operatorname{st}}\right\}\leftrightarrow\mathcal{EP}({\rm G}),

i.e. the ps-idempotents are given by endo-parameters after forgetting their Witt data. This is intended as a description of stable blocks in terms of endo-parameters and is asserted to be uniquely compatible with local Langlands.

Sources & referencesView supporting material

Primary source

David Helm, Robert Kurinczuk, Daniel Skodlerack and Shaun Stevens, “Block decompositions for p-adic classical groups and their inner forms”, arXiv:2405.13713 (2026).

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