Extended Sobolev scale for vector bundles, and its applications

We introduce an extended Sobolev scale for vector bundles over smooth closed manifolds and investigate its interpolation properties. This scale is built on the base of the inner product H\"ormander spaces whose order of regularity is given by an arbitrary positive function OR-varying at infinity in the sense of Avakumovi\'c. We prove that this scale is obtained by the interpolation with a function parameter between inner product Sobolev spaces, is closed with respect to the interpolation with a function parameter, and consists of all Hilbert spaces that are interpolation spaces between inner product Sobolev spaces. We also show that the spaces belonging to the scale introduced does not depend (up to equivalence of norms) on the choice of local charts on manifold and local trivializations of the bundle. Moreover, we prove embedding theorems and a duality theorem for this scale. We consider an elliptic pseudodifferential operators acting between vector bundles of the same rank on the extended Sobolev scale. We prove that this operator is bounded and Fredholm on pairs of appropriate H\"ormander spaces. An a priori estimate is established for the solutions and their local regularity is investigated. We also find new sufficient conditions for the solutions to have continuous derivatives of a given order.