A Polish group G is tame if for any continuous action of G, the corresponding orbit equivalence relation Borel. When [Formula: see text] countable abelian text], Solecki [Equivalence relations induced by actions groups, Trans. Amer. Math. Soc. 347 (1995) 4765–4777] gave a characterization when tame. In [L. Ding and S. Gao, Non-archimedean groups their actions, Adv. 307 (2017) 312–343], Gao show...
