Lothar Collatz

Lothar Collatz was a German mathematician, born in Arnsberg, Westphalia. In 1937 he posed the famous Collatz conjecture, which remains unsolved. The Collatz-Wielandt formula, for positive matrices important in the Perron–Frobenius theorem, is named after him. Collatz studied at different 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. For his many contributions to the field, Collatz had many honors bestowed upon him in his lifetime, including: election to the German Academy of Scientists Leopoldina, the academy at Bologna and Modena in Italy. honorary member of the Hamburg Mathematical Society honorary degrees by the University of São Paulo, the Technical University of Vienna, the University of Dundee in Scotland, Brunel University in England, the Technical University of Hanover, and the Technical University of Dresden. He died in Varna, Bulgaria, while attending a mathematics conference.