In celebration of Prof. Dr. Rolf Klötzler 65th birthday

Abstract

On January 11, 1996, Professor Klötzler celebrated his 65th birthday. This special issue of the journal “Optimization”, consisting of contributions by his friends, students and colleagues, is dedicated to him. Prof. Klötzler can proudly look back on forty successful years as a university teacher and mathematician. After positions at the Academy of Science, the Hochschule für Bauwesen in Leipzig and the Martin-Luther-University in Halle, where he was head of the Mathematics Institute from 1965 to 1971, he returned to the University of Leipzig in 1972 as a full Professor. He was a student there from 1949 to 1953 and had attended lectures by Ernst Hölder and Herbert Beckert. His scientific treatises are extremely extensive and have made great contributions to many branches of calculus of variations, optimal control and mathematical programming. The common thread running through his work is the solution of Hilbert’s problems concerning the calculus of variations and its development,control theory. Coming from the school of calculus of variations founded by Leon Lichtenstein and Otto Hölder in Leipzig, his scientific interest first focussed on questions concerning extension of field theory of calculus of variations and existence theory of global geodesic fields, from which optimality criteria could be derived. In addition, he was able to establish eigen value criteria for weak optimality of extremals of regular variational problems with multiple integrals. Fundamental results from these works appear in the frequently quoted textbook “MehrdimensionaleVariationsrechnung”, published in 1969.