Geometrical Characterizations of Biorthougonal Basis Systems in a Branch Space

摘要

Various characterizations of biorthogonal basis systems have been obtained in certain cases and their properties investigated [3, 4, 5, 6, 7]. In the present paper geometrical characterizations of biorthogonal basis systems will be discussed pursuing further the investigations initi¬ated in the author's note [2]. In particular it will be shown that the existence of a certain type of cone in the space will be necessary and sufficient that such a system exist.