Julius Wolff (mathematician)

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Julius Wolff , called Jules Wolff , (born April 18, 1882 in Nijmegen , † February 8, 1945 in Bergen-Belsen ) was a Dutch mathematician who dealt with analysis.

Life

Wolff, the son of the cattle dealer and butcher Levie Wolff and Ida Jacobsohn, studied mathematics and physics at the University of Amsterdam and received his doctorate in 1908 under Diederik Korteweg (dynames, understood as dual vectors (Dutch)). From 1907 to 1917 he taught as a teacher in Meppel , Middelburg and Amsterdam , became a private lecturer at the University of Groningen in 1917 and a lecturer at the University of Utrecht in 1922 . He also advised a life insurance company ( Eigen Hulp ) in The Hague . As a Jew, he was locked up in a concentration camp under National Socialist occupation and, after the family initially belonged to the Barneveld group of prominent Jews who were spared deportation, after they opted for the Gerzon group (the one for the clothing company Gerzon, which was considered essential to the war effort worked) deported to Bergen-Belsen, where he died. Even in the concentration camp and even in Bergen-Belsen, he is said to have worked on mathematical questions and given lectures.

His wife Betsy Gersons (1889–1945), the daughter of a clothing retailer, whom he married in Tilburg in 1911, and his son Ernst (1919–1945), who played the violin, also died in Bergen-Belsen in 1945 (about a month later). His son Louis died in Amsterdam in 1940. One daughter survived the war.

plant

Independently of Arnaud Denjoy, he proved the Denjoy and Wolff theorem in the iteration of holomorphic mappings of the open unit disk D. Let f be a holomorphic function that maps D to itself and is not a Möbius transformation (automorphism of the unit disk), then there is exactly one point P in the closure of D for which the iterates of f ( ) are uniformly on compact subsets of D. P converge (for P in D, P is a fixed point). If P is not in D, then every disk H in D that touches the unit circle in P is invariant under f.

He also wrote a Rand version of Schwarz's lemma (in connection with the proof of Denjoy and Wolff's theorem, which uses Schwarz's lemma).

The following theorem of topology comes from him: The location of points that are equidistant from two connected sets in the plane is a curve that is differentiable almost everywhere. He applied this to a new proof of Jordan's Curve Theorem .

In the theory of conformal mapping he introduced the angle derivation in an essay in 1926, independently of Edmund Landau , Georges Valiron and Constantin Caratheodory , the introduction of which attracted more attention a year later.

He was invited speaker at the International Congress of Mathematicians in Toronto in 1924 and in Zurich in 1932 .

literature

  • JA Barrau: In Memoriam Prof. Dr. J. Wolff, Nieuw Archief voor Wiskunde, Volume 22, 1948, pp. 113-114
  • Johannes van der Corput : Wiskunde, in: KF Proost, J. Romein: Geestelijk Nederland 1920–1940, Volume 2, Amsterdam: Kosmos 1948, pp. 255–291, to Wolff p. 279 f and reproduction of a portrait that fellow prisoners in Barneveld concentration camp 1943 made by him (p. 266), pdf
  • David Shoiket: Julia-Wolff-Caratheodory theorem, in Michiel Hazewinkel, Encyclopedia of Mathematics, Suppl. III, Kluwer 2001
  • M. Wolff: De nakomelingen van Wolff ben Eleazar en Moshe ben Gompertz Halevi, 1695-1995 , Arnheim, 2001, pp. 196-200

Fonts

  • Sur l'itération des fonctions holomorphes dans une région, et dont les valeurs appartiennent a cette région, Compte Rendus Acad. Sci. Paris, Volume 182, 1926, pp. 42-43
  • Sur l'itération des fonctions bornées, Rendus Acad. Sci. Paris, Volume 182, 1926, pp. 200-201
  • Sur une généralisation d'un théorème de Schwarz, Rendus Acad. Sci. Paris, Volume 182, 1926, pp. 918-920
  • Fourier series, with tasks, Groningen: Noordhoff 1931

Web links

Individual evidence

  1. ↑ Denjoy Sur l'itération des fonctions analytiques, Comptes Rendus Acad. Sci. Paris, Volume 182, 1926, pp. 255-257
  2. ↑ It is also dealt with in Norbert Steinmetz: Rational Iteration: complex analytic dynamical systems, De Gruyter 1993, p. 42f
personal data
SURNAME Wolff, Julius
ALTERNATIVE NAMES Wolff, Jules
BRIEF DESCRIPTION Dutch mathematician
DATE OF BIRTH April 18, 1882
PLACE OF BIRTH Nijmegen
DATE OF DEATH February 8, 1945
Place of death Bergen-Belsen