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

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Let (X,B,μ)(X,\mathcal{B},\mu) be a probability space, and let T,S:X→XT,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,g∈L∞(μ)f,g\in L^{\infty}(\mu),

lim⁡N→∞∥E⁡n∈[N]Tnf S⌊G(n)⌋g−E⁡[f∣IT]E⁡[g∣IS]∥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 A∈BA\in\mathcal{B},

lim⁡N→∞E⁡n∈[N]μ(A∩T−nA∩T−⌊G(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.

References

Primary source

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

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