Although the definition of the K-property seems reasonably general, it stands in sharp distinction to the Bernoulli automorphism. In particular, the Ornstein isomorphism theorem does not apply to K-systems, and so the entropy is not sufficient to classify such systems – there exist uncountably many non-isomorphic K-systems with the same entropy. In essence, the collection of K-systems is large, messy and uncategorized; whereas the B-automorphisms are 'completely' described by Ornstein theory.
Kolmogorov automorphisms are precisely the natural extensions of exact endomorphisms,[2] i.e. mappings for which consists of measure-zero sets or their complements, where is the sigma-algebra of measureable sets,.
Referencesedit
^Peter Walters, An Introduction to Ergodic Theory, (1982) Springer-Verlag ISBN0-387-90599-5
^V. A. Rohlin, Exact endomorphisms of Lebesgue spaces, Amer. Math. Soc. Transl., Series 2, 39 (1964), 1-36.
Further readingedit
Christopher Hoffman, "A K counterexample machine", Trans. Amer. Math. Soc.351 (1999), pp 4263–4280.
January 01, 1970
kolmogorov, automorphism, mathematics, automorphism, shift, system, invertible, measure, preserving, automorphism, defined, standard, probability, space, that, obeys, kolmogorov, zero, bernoulli, automorphisms, automorphisms, says, they, have, property, vice, . In mathematics a Kolmogorov automorphism K automorphism K shift or K system is an invertible measure preserving automorphism defined on a standard probability space that obeys Kolmogorov s zero one law 1 All Bernoulli automorphisms are K automorphisms one says they have the K property but not vice versa Many ergodic dynamical systems have been shown to have the K property although more recent research has shown that many of these are in fact Bernoulli automorphisms Although the definition of the K property seems reasonably general it stands in sharp distinction to the Bernoulli automorphism In particular the Ornstein isomorphism theorem does not apply to K systems and so the entropy is not sufficient to classify such systems there exist uncountably many non isomorphic K systems with the same entropy In essence the collection of K systems is large messy and uncategorized whereas the B automorphisms are completely described by Ornstein theory Contents 1 Formal definition 2 Properties 3 References 4 Further readingFormal definition editLet X B m displaystyle X mathcal B mu nbsp be a standard probability space and let T displaystyle T nbsp be an invertible measure preserving transformation Then T displaystyle T nbsp is called a K automorphism K transform or K shift if there exists a sub sigma algebra K B displaystyle mathcal K subset mathcal B nbsp such that the following three properties hold 1 K T K displaystyle mbox 1 mathcal K subset T mathcal K nbsp 2 n 0 T n K B displaystyle mbox 2 bigvee n 0 infty T n mathcal K mathcal B nbsp 3 n 0 T n K X displaystyle mbox 3 bigcap n 0 infty T n mathcal K X varnothing nbsp Here the symbol displaystyle vee nbsp is the join of sigma algebras while displaystyle cap nbsp is set intersection The equality should be understood as holding almost everywhere that is differing at most on a set of measure zero Properties editAssuming that the sigma algebra is not trivial that is if B X displaystyle mathcal B neq X varnothing nbsp then K T K displaystyle mathcal K neq T mathcal K nbsp It follows that K automorphisms are strong mixing All Bernoulli automorphisms are K automorphisms but not vice versa Kolmogorov automorphisms are precisely the natural extensions of exact endomorphisms 2 i e mappings T displaystyle T nbsp for which n 0 T n M displaystyle bigcap n 0 infty T n mathcal M nbsp consists of measure zero sets or their complements where M displaystyle mathcal M nbsp is the sigma algebra of measureable sets References edit Peter Walters An Introduction to Ergodic Theory 1982 Springer Verlag ISBN 0 387 90599 5 V A Rohlin Exact endomorphisms of Lebesgue spaces Amer Math Soc Transl Series 2 39 1964 1 36 Further reading editChristopher Hoffman A K counterexample machine Trans Amer Math Soc 351 1999 pp 4263 4280 Retrieved from https en wikipedia org w index php title Kolmogorov automorphism amp oldid 1145455971, wikipedia, wiki, book, books, library,