The Hahn-Banach Theorem and a Class of Non-Locally Convex Spaces.
The paper is concerned with the Fréchet differentiability and operator convexity of the operator functions on sets of self-adjoint operators on finite-dimensional inner product spaces which are associated with real-valued functions of one or two variables. In Part I it is shown that if a real-valued function is L times continuously differentiable then the associated operator functions are L times Fréchet differentiable with continuous Fréchet derivatives. It is shown that the operator functions...
It is shown that every closed rotation and translation invariant subspace of or , , is of spectral synthesis, i.e. is spanned by the polynomial-exponential functions it contains. It is a classical problem to find those measures of compact support on with the following property: (P) The only function satisfying for all rigid motions of is the zero function. As an application of the above result a characterization of such measures is obtained in terms of their Fourier-Laplace transforms....
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