Þráinn Eiríksson

Þráinn Eiríksson is an applied mathematician whose work sits where integrable systems meet high-accuracy scientific computing. Trained in Reykjavík and later in Copenhagen, he spent much of his career on the numerical treatment of dispersive nonlinear wave equations — the nonlinear Schrödinger and Gross–Pitaevskii equations above all — as they arise in nonlinear optics, cold-atom physics, and the study of rogue waves on deep water.

His method is old-fashioned in the best sense: reduce space to a high-order spectral operator, integrate the resulting system in time to an accuracy you can actually verify, and never trust a solution whose conserved quantities have quietly drifted. He treats the L² norm, momentum, and Hamiltonian energy as independent witnesses — held to a tolerance of 10⁻¹⁰ or better — on the principle that a solver which fails to conserve what the equation conserves has not solved anything.

He works in Python by preference and on principle: every figure and every reported number in this book is reproducible from its source. He lives between Reykjavík and the North Atlantic coast, where the sea still occasionally produces the waves he spends his days approximating.