Interpolative construction for operator ideals


Abstract


The problem from which this article originated is the following: given an operator T:E→ F between Banach spaces belonging simultaneously to two operator ideals, \mathcal A and \mathcal B say, when is it possible to find a decomposition T = A· B, where A∈ \mathcal A and B∈\mathcal B, or at least A∈ \dot{\mathcal{A}} and B∈ \ddot{\mathcal B}, with \dot{\mathcal{A}} and \ddot{\mathcal B} being associated with \mathcal A and \mathcal B in a specific sense? It was shown by S. Heinrich [2] that such a decomposition is always possible, with \mathcal A=\dot{\mathcal{A}} and \mathcal B=\ddot{\mathcal B},if \mathcal A and \mathcal B are uniformly closed, \mathcal A is surjective, and \mathcal B is injective.Heinrich’s arguments are based on a simple interpolation technique which appears to be strongy related to certain general constructions with operator ideals that were successfully applied in a seemingly different context in recent years (ref.[8],[5],and [4]-[7], [1]). We intend to investigate the fundamentals of such constructions and their interpolation-theoretic background in this paper, with emphasis on the impact to the factorization problem.Applications will be given for ideals generated by s-number sequences and to type p and cotype q operators.

DOI Code: 10.1285/i15900932v8n1p45

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