We prove a sharp pointwise estimate of the nonincreasing rearrangement of the fractional maximal function of ⨍, , by an expression involving the nonincreasing rearrangement of ⨍. This estimate is used to obtain necessary and sufficient conditions for the boundedness of between classical Lorentz spaces.
2000 Mathematics Subject Classification: 35L05, 35P25, 47A40.The problem studied here was suggested to us by V. Petkov. Since the beginning of our careers, we have benefitted from his insights in partial differential equations and mathematical physics. In his writings and many discussions, the conjuction of deep analysis and specially interesting problems has been a source inspiration for us.The research of J. Rauch is partially supported by the U.S. National Science Foundation under grant NSF-DMS-0104096...
We give a simple direct proof of the polar decomposition for separated linear maps in pseudo-Euclidean geometry.
Let be a locally compact Hausdorff space and let be the Banach space of all complex valued continuous functions vanishing at infinity in , provided with the supremum norm. Let be a quasicomplete locally convex Hausdorff space. A simple proof of the theorem on regular Borel extension of -valued -additive Baire measures on is given, which is more natural and direct than the existing ones. Using this result the integral representation and weak compactness of a continuous linear map when...
The nonhomogeneous backward Cauchy problem , where is a positive self-adjoint unbounded operator which has continuous spectrum and is a given function being given is regularized by the well-posed problem. New error estimates of the regularized solution are obtained. This work extends earlier results by N. Boussetila and by M. Denche and S. Djezzar.