On equivalence relations induced by locally compact TSI Polish groups admitting open identity component

Abstract

For a Polish group $G$, let $E(G)$ be the right coset equivalence relation $G^\omega/c(G)$, where $c(G)$ is the group of all convergent sequences in $G$. We prove a Rigid theorem on locally compact TSI Polish groups admitting open identity component, as follows: Let $G$ be a locally compact TSI Polish group such that $G_0$ is open in $G$, and let $H$ be a nontrivial pro-Lie TSI Polish group. Then $E(G)\leq_BE(H)$ iff there exists a continuous homomorphism $\phi:G_0\to H_0$ satisfying the following conditions: (i) $\ker(\phi)$ is non-archimedean; (ii) $\phi{\rm Inn}_G(G_0)\subseteq\overline{{\rm Inn}_H(H_0)\phi}$ under pointwise convergence topology. An application of the Rigid theorem yields a negative answer to Question 7.5 of [2].