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Generic behavior of a measure-preserving transformation

Published online by Cambridge University Press:  25 September 2018

MAHMOOD ETEDADIALIABADI*
Affiliation:
Department of Mathematics, University of Illinois, 1409 W. Green St., Urbana, IL 61801, USA email [email protected]

Abstract

Del Junco–Lemańczyk [Generic spectral properties of measure-preserving maps and applications. Proc. Amer. Math. Soc., 115 (3) (1992)] showed that a generic measure-preserving transformation satisfies certain orthogonality conditions. More precisely, there is a dense $G_{\unicode[STIX]{x1D6FF}}$ subset of measure preserving transformations such that, for every $T\in G$ and $k(1),k(2),\ldots ,k(l)\in \mathbb{Z}^{+}$, $k^{\prime }(1),k^{\prime }(2),\ldots ,k^{\prime }(l^{\prime })\in \mathbb{Z}^{+}$, the convolutions

$$\begin{eqnarray}\unicode[STIX]{x1D70E}_{T^{k(1)}}\ast \cdots \ast \unicode[STIX]{x1D70E}_{T^{k(l)}}\quad \text{and}\quad \unicode[STIX]{x1D70E}_{T^{k^{\prime }(1)}}\ast \cdots \ast \unicode[STIX]{x1D70E}_{T^{k^{\prime }(l^{\prime })}},\end{eqnarray}$$
where $\unicode[STIX]{x1D70E}_{T^{k}}$ is the maximal spectral type of $T^{k}$, are mutually singular, provided that $(k(1),k(2),\ldots ,k(l))$ is not a rearrangement of $(k^{\prime }(1),k^{\prime }(2),\ldots ,k^{\prime }(l^{\prime }))$. We will introduce analogous orthogonality conditions for continuous unitary representations of the group of all measurable functions with values in the circle, $L^{0}(\unicode[STIX]{x1D707},\mathbb{T})$, which we denote by the DL-condition. We connect the DL-condition with a result of Solecki [Unitary representations of the groups of measurable and continuous functions with values in the circle. J. Funct. Anal., 267 (2014), pp. 3105–3124] which identifies continuous unitary representations of $L^{0}(\unicode[STIX]{x1D707},\mathbb{T})$ with a collection of measures $\{\unicode[STIX]{x1D706}_{\unicode[STIX]{x1D705}}\}$, where $\unicode[STIX]{x1D705}$ runs over all increasing finite sequence of non-zero integers. In particular, we show that the ‘probabilistic’ DL-condition translates to ‘deterministic’ orthogonality conditions on the measures $\unicode[STIX]{x1D706}_{\unicode[STIX]{x1D705}}$. As a corollary, we show that the same orthogonality conditions as in the result by Del Junco–Lemańczyk hold for a generic unitary operator on a separable infinite-dimensional Hilbert space.

Type
Original Article
Copyright
© Cambridge University Press, 2018

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References

Choksi, J. R. and Nadkarni, M. G.. Baire category in spaces of measure, unitary operators and transformations. Proc. Int. Conf. on Invariant Subspaces and Allied Topics (New Delhi). Eds. Helson, H. and Yadav, B.. Narosa Publishing House, New Delhi, 1990, pp. 147163.Google Scholar
Cornfeld, I. P., Fomin, S. V. and Sinai, Y. G.. Ergodic Theory. Springer, New York, 1982.Google Scholar
Del Junco, A. and Lemańczyk, M.. Generic spectral properties of measure-preserving maps and applications. Proc. Amer. Math. Soc. 115(3) (1992), 725736.Google Scholar
Glasner, E. and Weiss, B.. Spatial and non-spatial actions of Polish groups. Ergod. Th. & Dynam. Sys. 24 (2005), 15211538.Google Scholar
Katok, A. B.. Combinatorial Constructions in Ergodic Theory and Dynamics (University Lecture Series, 30). American Mathematical Society, Providence, RI, 2003.Google Scholar
Kechris, A. S.. Global Aspects of Ergodic Group Actions (Mathematical Surveys and Monographs, 160). American Mathematical Society, Providence, RI, 2010.Google Scholar
King, J. L.. The generic transformation has roots of all orders. Colloq. Math.(84/85) (2000), 521547.Google Scholar
Melleray, J. and Tsankov, T.. Generic representations of abelian groups and extreme amenability. Israel J. Math. 198 (2013), 129167.Google Scholar
Nadkarni, M. G.. Spectral Theory of Dynamical Systems (Birkhäuser Advanced Texts Basler Lehrbücher). Birkhäuser, Basel, 1998.Google Scholar
Solecki, S.. Closed subgroups generated by generic measure automorphisms. Ergod. Th. & Dynam. Sys. 34 (2014), 10111017.Google Scholar
Solecki, S.. Unitary representations of the groups of measurable and continuous functions with values in the circle. J. Funct. Anal. 267 (2014), 31053124.Google Scholar
Stepin, A. M.. Spectral properties of generic dynamical systems. Math. USSR Izv. 29(1) (1987), 159192.Google Scholar