Pointwise ergodic theorem for locally countable quasi-pmp graphs
نویسندگان
چکیده
We prove a pointwise ergodic theorem for quasi-probability-measure-preserving (quasi-pmp) locally countable measurable graphs, equivalently, Schreier graphs of quasi-pmp actions groups. For the gives an increasing sequence Borel subgraphs with finite connected components over which averages any $ L^1 function converges to its expectation. This implies that every (not necessarily pmp) graph on standard probability space contains hyperfinite subgraph. A consequence this is treeable equivalence relation has free factor.The pmp case main was first proven by R. Tucker-Drob using deep result from theory. Our proof different: it self-contained and applies more generally graphs. Among other things, involves introducing invariant concerning asymptotic functions method tiling large part sets prescribed properties. The non-pmp setting additionally exploits new quasi-order called visibility analyze interplay between Radon–Nikodym cocycle structure, providing sufficient condition hyperfiniteness.
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ژورنال
عنوان ژورنال: Journal of Modern Dynamics
سال: 2022
ISSN: ['1930-5311', '1930-532X']
DOI: https://doi.org/10.3934/jmd.2022019