Minimal and Closest Points Nonexpansive and Quasi-Nonexpansive Retractions in Real Banach Spaces
Pier Luigi Papini · Birkhäuser Basel eBooks · 1983
The notions indicated in the title and related ones have been studied independently by various authors. Some characterizations of inner product spaces have been given in terms of properties of minimal and closest points, or by considering special retractions. Yet, the very strong connections existing among the above notions have not been considered in full. This present analysis shows that some results can be obtained from older ones, and other results can be restated in a sharper form using known facts and simple connections relating the various notions.