Collatz studied at universities in Germany including the
University of Greifswald and the
University of Berlin, where he was supervised by
Alfred Klose, receiving his doctorate in 1935 for a dissertation entitled
Das Differenzenverfahren mit höherer Approximation für lineare Differentialgleichungen (The finite difference method with higher approximation for linear differential equations). He then worked as an assistant at the University of Berlin, before moving to the
Technische Hochschule Karlsruhe (now
Karlsruhe Institute of Technology) in 1935 where he remained through 1937. From 1938 to 1943, he worked as a
Privatdozent in Karlsruhe. In the war years he worked with
Alwin Walther at the Institute for Practical Mathematics of the
Technische Hochschule Darmstadt. From 1943 to 1952, Collatz held a chair at the
Technische Hochschule Hannover (now
Leibniz University Hannover). From 1952 until his retirement in 1978, Collatz worked at the
University of Hamburg, where he founded the Institute of Applied Mathematics in 1953. After retirement as professor
emeritus, he continued to be very active at mathematical conferences. For his many contributions to the field, Collatz had many honors bestowed upon him in his lifetime, including: • election to the
Academy of Sciences Leopoldina, the
Academy of Sciences of the Institute of Bologna, and the Academy at Modena in Italy • honorary member of the
Hamburg Mathematical Society • honorary degrees from the
University of São Paulo, the
Vienna University of Technology, the
University of Dundee in
Scotland,
Brunel University in England, the
University of Hannover in 1981, and the
Technische Universität Dresden. He died unexpectedly from a heart attack in
Varna, Bulgaria, while attending a mathematics conference. ==Selected works==