English

Topological correspondence of multiple ergodic averages of nilpotent group actions

Dynamical Systems 2016-11-09 v2

Abstract

Let (X,Γ)(X,\Gamma) be a topological system, where Γ\Gamma is a nilpotent group generated by T1,,TdT_1,\ldots, T_d such that for each TΓT\in \Gamma, TeΓT\neq e_\Gamma, (X,T)(X,T) is weakly mixing and minimal. For d,kNd,k\in \mathbb{N}, let pi,j(n),1ik,1jdp_{i,j}(n), 1\le i\le k, 1\le j\le d be polynomials with rational coefficients taking integer values on the integers and pi,j(0)=0p_{i,j}(0)=0. We show that if the expressions gi(n)=T1pi,1(n)Tdpi,d(n)g_i(n)=T_1^{p_{i,1}(n)}\cdots T_d^{p_{i,d}(n)} depends nontrivially on nn for i=1,2,,ki=1,2,\cdots,k, and for all ij{1,2,,k}i\neq j\in \{1,2,\ldots,k\} the expressions gi(n)gj(n)1g_i(n)g_j(n)^{-1} depend nontrivially on nn, then there is a residual set X0X_0 of XX such that for all xX0x\in X_0 \begin{equation*} \{(g_1(n)x, g_2(n)x,\ldots, g_k(n)x)\in X^k:n\in \mathbb{Z}\} \end{equation*} is dense in XkX^k.

Keywords

Cite

@article{arxiv.1604.07113,
  title  = {Topological correspondence of multiple ergodic averages of nilpotent group actions},
  author = {Wen Huang and Song Shao and Xiangdong Ye},
  journal= {arXiv preprint arXiv:1604.07113},
  year   = {2016}
}

Comments

24 pages, revised version following referees' reports, to appear in Journal d'Analyse Mathematique