On spectral properties of linear combinations of idempotents
Hong-Ke Du, Chunyan Deng, Mostafa Mbekhta, Vladimír Müller · Studia Mathematica · 2007
Let $P,Q$ be two linear idempotents on a Banach space. We show that the closedness of the range and complementarity of the kernel (range) of linear combinations of $P$ and $Q$ are independent of the choice of coefficients. This generalizes known results a