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Strong convergence of alternating projections. (English) Zbl 07536869

Summary: In this paper, we provide a necessary and sufficient condition under which the method of alternating projections on Hadamard spaces converges strongly. This result is new even in the context of Hilbert spaces. In particular, we found the circumstance under which the iteration of a point by projections converges strongly and we answer partially the main question that motivated Bruck’s paper [J. Math. Anal. Appl. 88, 319–332 (1982; Zbl 0512.47042)]. We apply this condition to generalize Prager’s theorem for Hadamard manifolds and generalize Sakai’s theorem for a larger class of the sequences with full measure with respect to Bernoulli measure. In particular, we answer to a long-standing open problem concerning the convergence of the successive projection method [A. Aleyner and S. Reich, J. Convex Anal. 16, No. 3–4, 633–640 (2009; Zbl 1194.47061)]. Furthermore, we study the method of alternating projections for a nested decreasing sequence of convex sets on Hadamard manifolds, and we obtain an alternative proof of the convergence of the proximal point method.

MSC:

47Jxx Equations and inequalities involving nonlinear operators
28D05 Measure-preserving transformations
46N10 Applications of functional analysis in optimization, convex analysis, mathematical programming, economics
47H09 Contraction-type mappings, nonexpansive mappings, \(A\)-proper mappings, etc.
Full Text: DOI

References:

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