English

Locally divergent orbits of maximal tori and values of forms at integral points

Dynamical Systems 2018-03-09 v5

Abstract

Let \G\G be a semisimple algebraic group defined over a number field KK, \te\te a maximal KK-split torus of \G\G, S\mathcal{S} a finite set of valuations of KK containing the archimedean ones, \OO\OO the ring of S\mathcal{S}-integers of KK and KSK_\mathcal{S} the direct product of the completions Kv,vSK_v, v \in \mathcal{S}. Denote G=\G(KS)G = \G(K_\mathcal{S}), T=\te(KS)T = \te(K_\mathcal{S}) and Γ=\G(\OO)\Gamma = \G(\OO). Let Tπ(g)T\pi(g) be a locally divergent orbit for the action of TT on G/ΓG/\Gamma by left translations. We prove: (11) if #S=2\# S = 2 then the closure Tπ(g)\overline{T\pi(g)} is a union of finitely many TT-orbits all stratified in terms of parabolic subgroups of \G×\G\G \times \G and, therefore, Tπ(g)\overline{T\pi(g)} is homogeneous only if Tπ(g){T\pi(g)} is closed, (22) if #S>2\# \mathcal{S} > 2 and KK is not a CM\mathrm{CM}-field then Tπ(g)\overline{T\pi(g)} is squeezed between closed orbits of two reductive groups of equal semisimple ranks implying that Tπ(g)\overline{T\pi(g)} is homogeneous when \G=SLn\G = \mathbf{SL}_{n}. As an application, if f=(fv)vSKS[x1,,xn]f = (f_v)_{v \in \mathcal{S}} \in K_{\mathcal{S}}[x_1, \cdots, x_{n}], where fvf_v are non-pairwise proportional decomposable over KK homogeneous forms, then f(\OOn)f(\OO^{n}) is dense in KSK_{\mathcal{S}}.

Keywords

Cite

@article{arxiv.1502.02297,
  title  = {Locally divergent orbits of maximal tori and values of forms at integral points},
  author = {George Tomanov},
  journal= {arXiv preprint arXiv:1502.02297},
  year   = {2018}
}

Comments

The article is replaced by its revised version arXiv:1801.02497