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Rigorous theory for AAA-least squares (AAALS) on general domains

Develop a rigorous convergence and accuracy theory for AAA-least squares (AAALS), extending beyond special cases (disk or half-plane), and delineate conditions under which the method succeeds or fails.

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Background

AAALS leverages AAA-selected exterior poles and least-squares fitting of real parts to solve Laplace problems efficiently. The authors explicitly state that no theory has been developed beyond limited settings and note counterexamples showing occasional failure. A comprehensive theory would clarify performance across geometries (e.g., corners, inlets) and data.

References

No theory has yet been developed for AAALS beyond a couple of theorems \ccite{aaals} applying just on a disk or a half-plane together with counterexamples there showing that the method does not always work.

Applications of AAA rational approximation (2510.16237 - Nakatsukasa et al., 17 Oct 2025) in Section 30 Laplace problems and AAA least-squares