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تسجيل مستخدم جديدStrictly ergodic distal models and a new approach to the Host-Kra factors
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Cocycles are a key object in Antol{i}n Camarena and Szegedys (topological) theory of nilspaces. We introduce measurable counterparts, named nilcycles, enabling us to give conditions which guarantee that an ergodic group extension of a strictly ergodic distal system admits a strictly ergodic distal topological model, revisiting a problem studied by Lindenstrauss. In particular we show that if the base space is a dynamical nilspace then a dynamical nilspace topological model may be chosen for the extension. This approach combined with a structure theorem of Gutman, Manners and Varj{u} applied to the ergodic group extensions between successive Host-Kra characteristic factors gives a new proof that these factors are inverse limit of nilsystems.
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