Lothar Collatz
1910–1990, Arnsberg, Germany, Varna, Bulgaria
German mathematician who founded the Hamburg school of applied mathematics and, in 1937, posed the still-unsolved 3n+1 problem now known as the Collatz conjecture.
Lothar Collatz was a German mathematician who devoted his career to numerical analysis and applied mathematics. He studied at the universities of Greifswald, Munich, Göttingen and Berlin before completing a doctorate in Berlin in 1935 under Alfred Klose, with a dissertation on finite-difference methods for linear differential equations.
In 1937 he proposed a simple iterative rule, now known as the Collatz conjecture (the "3n+1 problem"): halve an even number, or triple an odd number and add one, and ask whether every starting value eventually reaches 1. Although only a minor note among his hundreds of papers, it became one of the most famous open problems in mathematics.
Collatz was appointed professor at the Technical University of Hanover in 1943 and, in 1952, moved to the University of Hamburg, where he founded the Institute of Applied Mathematics. He wrote influential textbooks on eigenvalue problems, functional analysis for numerical mathematics, and optimization, and his name is also attached to the Collatz–Wielandt formula in matrix theory.
Workplaces: Technical University of Hanover, University of Hamburg
Germany