Estimates for projections in Banach spaces and existence of direct complements

Gunther Dirr¹, Vladimir Rakočević², Harald K. Wimmer³
Studia Math. 170 (2005), 211-216
doi:10.4064/sm170-2-6

Abstract: 
Let $W$ and $L$ be complementary subspaces of a Banach space $X$ and let $P(W,L)$ denote the projection on $W$ along $L$. We obtain a sufficient condition for a subspace $M$ of $X$ to be complementary to $W$ and we derive estimates for the norm of $P(W,L) - P(W,M)$.

MSC (2000): Primary 46B20.
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Mathematisches Institut
Universität Würzburg
D-97074 Würzburg, Germany
Department of Mathematics
University of Niš
18000 Niš, Yugoslavia
Mathematisches Institut
Universität Würzburg
D-97074 Würzburg, Germany