Alternating projections and coupling slope

We consider the method of alternating projections for finding a point in the intersection of two possibly nonconvex closed sets. We present a local linear convergence result that makes no regularity assumptions on either set (unlike previous results), while at the same time weakening standard transversal intersection assumptions. The proof grows out of a study of the slope of a natural nonsmooth coupling function. When the two sets are semi-algebraic and bounded, we also prove subsequence convergence to the intersection with no transversality assumption.



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