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Ander Murua coauthored complex-coefficient operator splitting methods with Sergio Blanes and Fernando Casas. They analyze how composition coefficients influence order and error propagation. Positive real parts allow complex-time substeps to bypass an obstruction associated with negative real coefficients, particularly relevant to dissipative evolution equations.^[ref]

Fernando Casas studied operator splitting with Sergio Blanes and Ander Murua. Their work constructs higher-order compositions using complex coefficients with positive real parts. The approach addresses the negative-step obstruction of real-coefficient splittings, making high-order integration possible in settings where backward evolution, such as backward diffusion, is problematic.^[ref]