We study the class of all rearrangement-invariant ( = r.i.) function spaces E on [0,1] such that there exists 0 < q < 1 for which , where is an arbitrary sequence of independent identically distributed symmetric random variables on [0,1] and C > 0 does not depend on n. We completely characterize all Lorentz spaces having this property and complement classical results of Rodin and Semenov for Orlicz spaces , p ≥ 1. We further apply our results to the study of Banach-Saks index sets in r.i. spaces.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-sm191-2-1, author = {F. A. Sukochev and D. Zanin}, title = {Khinchin inequality and Banach-Saks type properties in rearrangement-invariant spaces}, journal = {Studia Mathematica}, volume = {192}, year = {2009}, pages = {101-122}, zbl = {1175.46018}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm191-2-1} }
F. A. Sukochev; D. Zanin. Khinchin inequality and Banach-Saks type properties in rearrangement-invariant spaces. Studia Mathematica, Tome 192 (2009) pp. 101-122. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm191-2-1/