The explicit characterization of coefficients of a.e. convergent orthogonal series
In this note, the author presents a complete characterization of sequences \((a_{n})\) for which \(\sum_{n\geq 1} a_{n}\,\Phi_{n}\) converges a.e for any orthonormal system \((\Phi_{n})\) in any \(L_{2}\)-space.
almost everywhere convergence of orthogonal series
scientific article; zbMATH DE number 5625427