English

On definable $f$-generic groups and minimal flows in $p$-adically closed fields

Logic 2023-11-01 v1

Abstract

Let XX be a definable group definable over a small model M0M_0. Recall that a global type pp on XX is definable ff-generic over M0M_0 if every left translate of pp is definable over M0M_0. We call pp strongly ff-generic over M0M_0 if every left translate of pp does not fork over M0M_0. Let HH be a group definable over the field Qp{\mathbb Q}_p of pp-adic numbers admitting global definable ff-generic types over Qp{\mathbb Q}_p. We show that HH has unboundedly many global weakly generic types iff there is a global type rr on HH which is strongly ff-generic over Qp{\mathbb Q}_p and a Qp{\mathbb Q}_p-definable function θ\theta such that θ(r)\theta(r) is finitely satisfiable in Qp{\mathbb Q}_p. Recall that the μ\mu-type μ(x)\mu(x) on HH is the partial type consisting of the formulas over Qp{\mathbb Q}_p which define open neighborhoods of the identity of HH. We show that every global weakly generic type rr on HH is μ\mu-invariant: For any ϵμ\epsilon\models \mu and ara\models r, we have ϵar\epsilon\cdot a\models r. Let GG be groups definable over Qp{\mathbb Q}_p such that HH is a normal subgroup of GG and G/HG/H is a definably compact group. Then we show that the weakly generic types on GG coincide with almost periodic types GG iff GG has boundedly many global weakly generic types.

Keywords

Cite

@article{arxiv.2310.20110,
  title  = {On definable $f$-generic groups and minimal flows in $p$-adically closed fields},
  author = {Ningyuan Yao and Zhentao Zhang},
  journal= {arXiv preprint arXiv:2310.20110},
  year   = {2023}
}
R2 v1 2026-06-28T13:06:51.131Z