Abstract
It is known that the unit ball in infinitely dimensional Hilbert space can be retracted onto its boundary via a lipschitzian mapping. The magnitude of Lipschitz constant is only roughly estimated. The note contains a number of observations connected to this result and opens some new problems.
Citation
Phichet Chaoha. Kazimierz Goebel. Imchit Termwuttipong. "Around Ulam's question on retractions." Topol. Methods Nonlinear Anal. 40 (1) 215 - 224, 2012.
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