English

On relative cuspidality

Representation Theory 2026-05-18 v2

Abstract

Let (G,H)(\mathbb{G},\mathbb{H}) be a symmetric pair of reductive groups over a pp-adic field with p2p\neq 2, attached to the involution θ\theta. Under the assumption that there exists a maximally θ\theta-split torus in G\mathbb{G}, which is anisotropic modulo its intersection with the split component of G\mathbb{G}, we extend Beuzart-Plessis' proof of existence of cuspidal representations, and prove that G(F)\mathbb{G}(F) admits strongly relatively cuspidal representations. This confirms expectations of Kato and Takano.

Keywords

Cite

@article{arxiv.2506.08393,
  title  = {On relative cuspidality},
  author = {Nadir Matringe},
  journal= {arXiv preprint arXiv:2506.08393},
  year   = {2026}
}

Comments

Main theorem wrong. (GL4n,Sp4n) provides a counter-example due to Lapid-Offen's classification of relative discrete series: none is strongly relatively cuspidal but there are G^- elliptic tori. Mistake in Section 7: \mu cannot be chosen uniform with respect to all parabolics. The first 6 sections might help prove existence of relatively cuspidal representations, but we did not find how

R2 v1 2026-07-01T03:08:16.694Z