Perturbation of ${\ell }_1$-copies in Preduals of JBW${}^{\ast }$-triples

Antonio M. Peralta, Hermann Pfitzner

Two normal functionals on a JBW${}^{\ast }$-triple are known to be orthogonal if and only if they are $L$-orthogonal (meaning that they span an isometric copy of ${\ell }_1(2)$). This is show…