Optimal Recovery of Mappings According to the Linear Data, Optimal Information Operators, and Extremal Subspaces
摘要
We consider the problems of optimal recovery of an operator A (generally speaking, nonlinear) defined on a unit ball BH in a Hilbert space H based on the information about elements of this unit ball BH given by a bounded linear operator T : H → Y, where Y is a Banach space. For a fixed information operator T, it is shown that the optimal method of recovery is offered by the so-called T-interpolating splines. For fixed Y, we also solve the problem of finding the optimal information operator. Moreover, for a bounded linear self-adjoint operator A, it is shown that if T is the optimal information operator for the recovery of A on BH, then any other operator TAn, n ∈ ℕ, is also the optimal information operator.