Hereditarily indecomposable Banach space
ID: hereditarily-indecomposable-banach-space
An infinite-dimensional Banach space is hereditarily indecomposable if no closed infinite-dimensional subspace is a topological direct sum of two infinite-dimensional closed subspaces. Equivalently, for any two infinite-dimensional closed subspaces and any , some unit vectors satisfy . A positive lower bound on such distances would make the addition map from an isomorphism onto a closed subspace.
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