Abstract
We prove a van der Corput-type lemma for power bounded Hilbert space operators. As a corollary we show that \(N^{-1}\sum _{n=1}^N T^{p(n)}\) converges in the strong operator topology for all power bounded Hilbert space operators T and all polynomials p satisfying \(p(\mathbb {N}_0)\subset \mathbb {N}_0\). This generalizes known results for Hilbert space contractions. Similar results are true also for bounded strongly continuous semigroups of operators.
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Berend, D., Lin, M., Rosenblatt, J., Tempelman, A.: Modulated and subsequential ergodic theorems in Hilbert and Banach spaces. Ergod. Theory Dyn. Syst. 22, 1653–1665 (2002)
Bergelson, V., Leibman, A., Moreira, C.G.: From discrete-to continuous-time ergodic theorems. Ergod. Theory Dyn. Syst. 32, 386–426 (2012)
Blum, J., Eisenberg, B.: Generalized summing sequences and the mean ergodic theorem. Proc. Am. Math. Soc. 42, 423–429 (1974)
Einsiedler, M., Ward, T.: Ergodic Theory with a View Towards Number Theory. Graduate Texts in Mathematics, vol. 259. Springer, London (2011)
Engel, K.-J., Nagel, R.: One-Parameter Semigroups for Linear Evolution Equations. Graduate Texts in Mathematics, vol. 194. Springer, New York (2000)
Jones, L.K., Lin, M.: Unimodular eigenvalues and weak mixing. J. Funct. Anal. 35, 42–48 (1980)
Kunszenti-Kovács, D., Nittka, R., Sauter, M.: One the limits of Cesàro means of polynomial powers. Math. Z. 268, 771–776 (2011)
Krengel, U.: Ergodic Theorems. De Gruyter Studies in Mathematics, vol. 6. Walter de Gruyter & Co., Berlin (1985)
Acknowledgments
The paper was written during the second named author’s stay at the University of Auckland. He wishes to thank for the warm hospitality and perfect working conditions there. The stay was supported by Grants IRSES, 14-07880S of GA ČR and RVO: 67985840.
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ter Elst, A.F.M., Müller, V. A van der Corput-type lemma for power bounded operators. Math. Z. 285, 143–158 (2017). https://doi.org/10.1007/s00209-016-1701-2
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DOI: https://doi.org/10.1007/s00209-016-1701-2