On invariant operator ranges
Eric Nordgren, Mehdi Radjabalipour, Heydar Radjavi, Peter Rosenthal · Transactions of the American Mathematical Society · 1979
A matricial representation is given for the algebra of operators leaving a given dense operator range invariant. It is shown that every operator on an infinite-dimensional Hilbert space has an uncountable family of invariant operator ranges, any two of which intersect only in 0.