Institution: | Department of Mathematics, North Dakota State University, Fargo, North Dakota 58105 Michael Lin ; Department of Mathematics, Ben Gurion University of the Negev, Beer Sheva, Israel James Olsen ; Department of Mathematics, North Dakota State University, Fargo, North Dakota 58105 |
Abstract: | It is shown that any bounded weight sequence which is good for all probability preserving transformations (a universally good weight) is also a good weight for any -contraction with mean ergodic (ME) modulus, and for any positive contraction of with . We extend the return times theorem by proving that if is a Dunford-Schwartz operator (not necessarily positive) on a Lebesgue space, then for any bounded measurable is a universally good weight for a.e. We prove that if a bounded sequence has "Fourier coefficents", then its weighted averages for any -contraction with mean ergodic modulus converge in -norm. In order to produce weights, good for weighted ergodic theorems for -contractions with quasi-ME modulus (i.e., so that the modulus has a positive fixed point supported on its conservative part), we show that the modulus of the tensor product of -contractions is the product of their moduli, and that the tensor product of positive quasi-ME -contractions is quasi-ME. |