English

Kazhdan isomorphism over families and integrality under close local fields

Representation Theory 2025-04-29 v1

Abstract

Let GG be a split connected reductive group defined over Z\mathbb{Z}. Let FF be a locally compact non-Archimedean field with residue characteristic pp. For a locally compact non-Archimedean field FF' that is sufficiently close to FF, D.Kazhdan establishes an isomorphism between the Hecke algebras H(G(F),Km)\mathcal{H}(G(F),K_m) and H(G(F),Km)\mathcal{H}(G(F'),K_m') with coefficients in C\mathbb{C}, where KmK_m (resp. KmK_m') is the mm-th congruence subgroup of G(F)G(F) (resp. G(F)G(F')). This result is generalised to arbitrary connected reductive algebraic groups by R.Ganapathy. In this article, we extend the result further where the coefficient ring of the Hecke algebras is considered to be more general, namely Noetherian Zl\mathbb{Z}_l-algebras with lpl\ne p. Then we use this isomorphism to prove certain compatibility result in the context of ll-adic representation theory.

Keywords

Cite

@article{arxiv.2504.18893,
  title  = {Kazhdan isomorphism over families and integrality under close local fields},
  author = {Sabyasachi Dhar},
  journal= {arXiv preprint arXiv:2504.18893},
  year   = {2025}
}

Comments

10 pages, Preliminary version. Comments are welcome