Onn's weak conjecture on representations of general linear groups over local rings

Let FF and FF' be non-Archimedean local fields with rings of integers o\mathfrak{o} and o\mathfrak{o}' having the same finite residue cardinality qq. For fixed integers n,r1n,r\geq 1, write or=o/pr\mathfrak{o}_r=\mathfrak{o}/\mathfrak{p}^r and or=o/(p)r\mathfrak{o}'_r=\mathfrak{o}'/(\mathfrak{p}')^r, and let Irr(G)\operatorname{Irr}(G) denote the irreducible complex representations of a group GG up to isomorphism.

Onn's weak conjecture. There is an isomorphism of group algebras

C[GLn(or)]C[GLn(or)],\mathbb{C}[\mathrm{GL}_n(\mathfrak{o}_r)]\cong\mathbb{C}[\mathrm{GL}_n(\mathfrak{o}'_r)],

or equivalently, a dimension-preserving bijection

Irr(GLn(or))Irr(GLn(or)).\operatorname{Irr}(\mathrm{GL}_n(\mathfrak{o}_r))\longleftrightarrow\operatorname{Irr}(\mathrm{GL}_n(\mathfrak{o}'_r)).

This conjecture asserts that the complex representation dimensions of these general linear groups depend only on the residue cardinality, not on the local field. It is presented as a conjecture of Onn; the source does not state a resolution.

Sources & referencesView supporting material

Primary source

Alexander Jackson, “A Polynomial Result for Dimensions of Irreducible Representations of Smooth Affine Group Schemes Over Principal Ideal Local Rings”, arXiv:2405.13724 (2024).

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