English

Divergence of weighted square averages in $L^1$

Dynamical Systems 2021-03-05 v3 Classical Analysis and ODEs Functional Analysis

Abstract

We study convergence of ergodic averages along squares with polynomial weights. For a given polynomial PZ[]P\in \mathbb{Z}[\cdot], consider the set of all θ[0,1)\theta\in[0,1) such that for every aperiodic system (X,μ,T)(X,\mu, T) there is a function fL1(X,μ)f\in L^1(X,\mu) such that the weighted averages along squares 1Nn=1Ne(P(n)θ)Tn2f {\frac{1}{N}\sum_{n=1}^N} e(P(n)\theta)T^{n^2}f diverge on a set with positive measure. We show that this set is residual and includes the rational numbers as well as a dense set of Liouville numbers. This on one hand extends the divergence result for squares in L1L^1 of the first author and Mauldin and on the other hand shows that the convergence result for linear weights for squares due to the second author and Krause in LpL^p, p>1p>1 does not hold for p=1p=1.

Keywords

Cite

@article{arxiv.1907.11060,
  title  = {Divergence of weighted square averages in $L^1$},
  author = {Zoltán Buczolich and Tanja Eisner},
  journal= {arXiv preprint arXiv:1907.11060},
  year   = {2021}
}

Comments

Slightly updated version after the second (very likely the last) report of the referee