We consider Littlewood-Paley functions associated with a non-isotropic dilation group on . We prove that certain Littlewood-Paley functions defined by kernels with no regularity concerning smoothness are bounded on weighted spaces, , with weights of the Muckenhoupt class. This, in particular, generalizes a result of N. Rivière (1971).
Let s ∈ ℝ, p ∈ (0,1] and q ∈ [p,∞). It is proved that a sublinear operator T uniquely extends to a bounded sublinear operator from the Triebel-Lizorkin space to a quasi-Banach space ℬ if and only if sup: a is an infinitely differentiable (p,q,s)-atom of < ∞, where the (p,q,s)-atom of is as defined by Han, Paluszyński and Weiss.
Let be a non-zero positive vector of a Banach lattice , and let be a positive linear operator on with the spectral radius . We find some groups of assumptions on , and under which the inequalities hold. An application of our results gives simple upper and lower bounds for the spectral radius of a product of positive operators in terms of positive eigenvectors corresponding to the spectral radii of given operators. We thus extend the matrix result obtained by Johnson and Bru which...
Bourgain’s discretization theorem asserts that there exists a universal constant with the following property. Let be Banach spaces with . Fix and set . Assume that is a -net in the unit ball of and that admits a bi-Lipschitz embedding into with distortion at most . Then the entire space admits a bi-Lipschitz embedding into with distortion at most . This mostly expository article is devoted to a detailed presentation of a proof of Bourgain’s theorem.We also obtain an improvement...