Abstract
We in this paper study the nonexpansive operators equipped with arbitrary metric and investigate the connections between firm nonexpansiveness, cocoerciveness and averagedness. The convergence of the associated fixed-point iterations is discussed with particular focus on the case of degenerate metric, since the degeneracy is often encountered when reformulating many existing first-order operator splitting algorithms as a metric resolvent. This work paves a way for analyzing the generalized proximal point algorithm with a non-trivial relaxation step and degenerate metric.
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Notes
This line of reasoning is very similar to Fejér monotonicity, see [5, Proposition 5.4, Theorem 5.5] for example.
Here, the functions f and g are assumed to be proper, lower semi-continuous and convex.
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Xue, F. On the Nonexpansive Operators Based on Arbitrary Metric: A Degenerate Analysis. Results Math 77, 237 (2022). https://doi.org/10.1007/s00025-022-01766-6
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DOI: https://doi.org/10.1007/s00025-022-01766-6