Preface: Introduction to special issue: In memory of Ludwig Faddeev

Ludwig Faddeev made fundamental contributions to the development of a number of areas of mathematical physics. There are several major topics in mathematical physics that originated with work by Faddeev or were revolutionized by his and his school’s results. Notable examples are mathematical scattering theory which includes inverse scattering theory for 1D and 3D Schrodinger operators, trace formulae, and the solution of the quantum 3 body problem; quantization of the Yang-Mills field; spectral theory of automorphic functions; pioneering works on the inverse scattering method in soliton theory; the quantum inverse scattering method and quantum groups. Faddeev also was a visionary who had a unique understanding of the discipline as a whole, with all its profound theoretical physics and pure mathematical connections. For a detailed exposition of Faddeev’s outstanding achievements, see the recent survey.40