文摘
We describe the one-dimensional Čebyšëv subspaces of a JBW∗-triple M by showing that for a non-zero element x in M, \(\mathbb{C}x\) is a Čebyšëv subspace of M if and only if x is a Brown-Pedersen quasi-invertible element in M. We study the Čebyšëv JBW∗-subtriples of a JBW∗-triple M. We prove that for each non-zero Čebyšëv JBW∗-subtriple N of M, exactly one of the following statements holds: (a) N is a rank-one JBW∗-triple with \(\dim(N)\geq2\) (i.e., a complex Hilbert space regarded as a type 1 Cartan factor). Moreover, N may be a closed subspace of arbitrary dimension and M may have arbitrary rank;