English

Local-global principle for congruence subgroups of Chevalley groups

Rings and Algebras 2015-11-24 v2

Abstract

We prove Suslin's local-global principle for principal congruence subgroups of Chevalley groups. Let GG be a Chevalley--Demazure group scheme with a root system ΦA1\Phi\ne A_1 and EE its elementary subgroup. Let RR be a ring and II an ideal of RR. Assume additionally that RR has no residue fields of 2 elements if Φ=C2\Phi=C_2 or G2G_2. Theorem. Let gG(R[X],XR[X])g\in G(R[X],XR[X]). Suppose that for every maximal ideal \m\m of RR the image of gg under the localization homomorphism at \m\m belongs to E(R\m[X],IR\m[X])E(R_\m[X],IR_\m[X]). Then, gE(R[X],IR[X])g\in E(R[X],IR[X]). The theorem is a common generalization of the result of E.Abe for the absolute case (I=RI=R) and H.Apte--P.Chattopadhyay--R.Rao for classical groups. It is worth mentioning that for the absolute case the local-global principle was obtained by V.Petrov and A.Stavrova in more general settings of isotropic reductive groups.

Keywords

Cite

@article{arxiv.1211.3575,
  title  = {Local-global principle for congruence subgroups of Chevalley groups},
  author = {Himanee Apte and Alexei Stepanov},
  journal= {arXiv preprint arXiv:1211.3575},
  year   = {2015}
}

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9 pages