Interpolation between sum and intersection of Banach spaces (Q1098072)

Let \(A_ 0\) and \(A_ 1\) be a compatible Banach couple. The author studies intermediate Banach spaces between the Banach couple \((A_ 0\cap A_ 1,A_ 0+A_ 1)\). In particular a result of \textit{N. Aronszajn} and \textit{E. Gagliardo} [Ann. Mat. Pura Appl., IV. Ser. 68, 51-118 (1965; Zbl 0195.131)], that gives a characterization of these spaces, is applied to symmetric spaces.