Exponential Riesz bases of subspaces and divided differences
نویسندگان
چکیده
Linear combinations of exponentials e iλ k t in the case where the distance between some points λ k tends to zero are studied. D. Ull-rich [30] has proved the basis property of the divided differences of exponentials in the case when {λ k } = Λ (n) and the groups Λ (n) consist of equal number of points all of them are close enough to n, n ∈ Z. We have generalized this result for groups with arbitrary number of close points and obtained a full description of Riesz bases of exponential divided differences.
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