Lothar Collatz


Lothar Collatz was a German mathematician, born in Arnsberg, Westphalia.
The problem is also known as the Collatz conjecture, named after him and still unsolved. The Collatz–Wielandt formula for the Perron–Frobenius eigenvalue of a positive square matrix was also named after him.
Collatz's 1957 paper with Ulrich Sinogowitz, who had been killed in the bombing of Darmstadt in World War II, founded the field of spectral graph theory.

Biography

Collatz studied at universities in Germany including the University of Berlin under Alfred Klose, receiving his doctorate in 1935 for a dissertation entitled Das Differenzenverfahren mit höherer Approximation für lineare Differentialgleichungen. He then worked as an assistant at the University of Berlin, before moving to the Technical University of Karlsruhe in 1935. There he also habilitated in 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 1952 until his retirement 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 on mathematical conferences.
For his many contributions to the field, Collatz had many honors bestowed upon him in his lifetime, including:
He died unexpectedly from a heart attack in Varna, Bulgaria, while attending a mathematics conference.

Selected works