Descriptors: Feller semigroups; Subordination in the sense of Bochner; Pseudo-differential operators with negative definite symbols of variable order; Hoh?s symbolic calculus
Abstrakt: We introduce a notion of regularity for coherent sheaves on Grassmannians of lines. We use this notion to prove some extension of Evans-Griffith criterion to characterize direct sums of line bundles. We also give. in the line of previous results by Costa and Miro-Roig, a cohomological characterization of exterior and symmetric powers of the universal bundles of the Grassmannian.
Descriptors: Besov spaces; Lorentz spaces; Embedding norms; Rates of blow-up
Abstrakt: Sharp estimates are obtained for the rates of blow up of the norms of embeddings of Besov spaces in Lorentz spaces as the parameters approach critical values.
