Averaging and recurrence conjecture for zero-entropy systems along superpolynomial times

Let (X,B,μ)(X,\mathcal{B},\mu) be a probability space, and let T,S:XXT,S:X\to X be two not necessarily commuting measure-preserving transformations. Let 0<c<1/20<c<1/2, and suppose that (X,μ,T)(X,\mu,T) has zero entropy. Write IT\mathcal{I}_T and IS\mathcal{I}_S for the σ\sigma-algebras of TT-invariant and SS-invariant sets, respectively. Averaging and recurrence conjecture. For every f,gL(μ)f,g\in L^{\infty}(\mu),

limNEn[N]TnfSG(n)gE[fIT]E[gIS]2=0,\lim_{N\to\infty}\left\|\operatorname*{\mathbb{E}}_{n\in[N]}T^nf\,S^{\lfloor G(n)\rfloor}g-\operatorname*{\mathbb{E}}[f\mid\mathcal{I}_T]\operatorname*{\mathbb{E}}[g\mid\mathcal{I}_S]\right\|_2=0,

where the limit is in L2(μ)L^2(\mu); and for every ABA\in\mathcal{B},

limNEn[N]μ(ATnATG(n)A)μ(A)3.\lim_{N\to\infty}\operatorname*{\mathbb{E}}_{n\in[N]}\mu\bigl(A\cap T^{-n}A\cap T^{-\lfloor G(n)\rfloor}A\bigr)\geq\mu(A)^3.

These conclusions are presented as a likely consequence of the preceding pointwise Furstenberg-system conjecture, so their status is conditional and not established in the supplied text.

Sources & referencesView supporting material

Primary source

Andreu Ferré Moragues and Andreas Koutsogiannis, “Furstenberg systems of certain sequences of superpolynomial growth”, arXiv:2510.11957 (2025).

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