Ernst Jacobsthal Über die Funktionalgleichung f(x+y) = f(x) + f(y) m.fl.

Abstract

Ernst Jacobsthal (1882 – 1965) got his mathematical education in Berlin, with Staatsexamen and Doctor’s degree as natural conclusions. He had a promising start, obtaining positions as Studienrat, Privatdozent and ausserordentlicher Professor. But it did not take long before he could feel the consequences of him being of Jewish decent and the leadership of Germany was taken over by the nazies. He lost his jobs, and had to leave the country. After a formal divorce from his wife Annemarie, who was not Jewish and remained in Berlin to take care of their belongings, he took off, and ended for different reasons in Trondheim. There he got friends and coworkers, and was happy, except for missing Annemarie. But soon it became dangerous for him even in Trondheim, and following an advice from Ralph Tambs Lyche, smuggled out from the concentration camp Falstad, where he was a prisoner of the German police, Jacobsthal escaped to Sweden. Here he stayed the rest of the time of the war in Europe, working partly on his own, partly with Trygve Nagell. When the war in Europe was over, he went back to Trondheim for a reunion with Annemarie. The practical difficulties they had at first were more than compensated by all friendships they met and their own great attitude. And soon they got a fine apartment near NTH, and Ernst got a personal position as dosent (associate professor). They went into a great period with a lot of good friends, and Ernst was extremely productive in his mathematics, and he published more papers than anyone else in DKNVS Forhandlinger and Skrifter.The very last paper came after his death, by help of Sigmund Selberg. Unfortunately Ernst’s health deteriorated.He was hospitalized, and after a while they had to leave for a warmer place, which was Überlingen by the Bodensee. That was their last home. Except for health problems, they were happy there, and Ernst went on with his mathematics all the time.