| |
|
Paul Hagelstein and Ioannis Parissis
Hölder continuity of Tauberian constants associated with discrete and ergodic strong maximal operators view print
|
|
Published: |
September 13, 2017
|
Keywords: |
ergodic theory, maximal operators, Kakutani-Rokhlin lemma, nonperiodic transformation |
Subject: |
Primary 37A25, Secondary: 42B25 |
|
|
Abstract
This paper concerns the smoothness of Tauberian constants of maximal operators in the discrete and ergodic settings. In particular, we define the discrete strong maximal operator \tilde{M}S on Zn by
\tilde{M}Sf(m) :=
sup0 ∈ R ⊂ Rn(1/#(R ∩ Zn))∑ j∈ R ∩ Zn |f(m+j)|, m∈ Zn,
where the supremum is taken over all open rectangles in Rn containing the origin whose sides are parallel to the coordinate axes. We show that the associated Tauberian constant \tilde{C}S(α), defined by
\tilde{C}S(α) := supE ⊂ Zn, 0 < #E < ∞ (1/#E)#{m ∈ Zn: \tilde{M}SϗE(m) > α},
is Hölder continuous of order 1/n. Moreover, letting U1, ..., Un denote a nonperiodic collection of commuting invertible transformations on the nonatomic probability space (Ω, Σ, μ) we define the associated maximal operator M ∗S by
M∗Sf(ω) :=
sup0 ∈ R ⊂ Rn (1/#(R ∩ Zn))∑(j1, ..., jn)∈ R|f(U1j1... Unjnω)|, ω∈Ω.
Then the corresponding Tauberian constant C∗S(α), defined by
C∗S(α) := supE ⊂ Ω, μ(E) > 0 (1/μ(E))μ({ω ∈ Ω : M∗SϗE(ω) > α}),
also satisfies C∗S ∈ C1/n(0,1). We will also see that, in the case n=1, that is in the case of a single invertible, measure preserving transformation, the smoothness of the corresponding Tauberian constant is characterized by the operator enabling arbitrarily long orbits of sets of positive measure.
|
|
Acknowledgements
P. H. is partially supported by a grant from the Simons Foundation (#521719 to Paul Hagelstein). I. P. is supported by grant MTM2014-53850 of the Ministerio de Economía y Competitividad (Spain), grant IT-641-13 of the Basque Government, and IKERBASQUE
|
|
Author information
Paul Hagelstein:
Department of Mathematics, Baylor University, Waco, Texas 76798
paul_hagelstein@baylor.edu
Ioannis Parissis:
Departamento de Matemáticas, Universidad del Pais Vasco, Aptdo. 644, 48080 Bilbao, Spain and Ikerbasque, Basque Foundation for Science, Bilbao, Spain
ioannis.parissis@ehu.es
|
|