Rolf Nevanlinna
| Rolf Nevanlinna | |
|---|---|
Rolf Nevanlinna with his friend Erik W. Tawaststjerna at the piano (1962).
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| Native name | Rolf Herman Neovius |
| Born |
22 October 1895 Joensuu |
| Died | 28 May 1980 (aged 84) Helsinki |
| Nationality | Finnish |
| Fields | Mathematics |
| Institutions | University of Helsinki |
| Alma mater | University of Helsinki |
| Doctoral advisor | Ernst Leonard Lindelöf |
| Doctoral students |
Lars Ahlfors Kari Karhunen Gustav Elfving Olli Lehto Ilppo Simo Louhivaara Leo Sario Inkeri Simola |
| Known for | Nevanlinna theory |
Rolf Herman Nevanlinna (22 October 1895 – 28 May 1980) was one of the most famous Finnish mathematicians. He was particularly appreciated for his work in complex analysis.
Rolf Nevanlinna studied at the University of Helsinki. He graduated in 1917. He obtained his doctorate in 1919 with the thesis Über beschränkte Funktionen die in gegebenen Punkten vorgeschriebene Werte annehmen; his thesis advisor was Ernst Lindelöf. In 1922 he was appointed a docent in the University of Helsinki, and in 1926 he was given a newly created full professorship in Helsinki. From 1947 Nevanlinna had a chair in the University of Zurich, which he held on a half-time basis after receiving in 1948 a permanent position as one of the 12 salaried Academicians in the newly created Academy of Finland.
Rolf Nevanlinna's most important mathematical achievement is the value distribution theory of meromorphic functions. The roots of the theory go back to the result of Émile Picard in 1879, showing that a non-constant complex-valued function which is analytic in the entire complex plane assumes all complex values save at most one. In the early 1920s Rolf Nevanlinna, partly in collaboration with his brother Frithiof, extended the theory to cover meromorphic functions, i.e. functions analytic in the plane except for isolated points in which the Laurent series of the function has a finite number of terms with a negative power of the variable. Nevanlinna's value distribution theory or Nevanlinna theory is crystallized in its two Main Theorems. Qualitatively, the first one states that if a value is assumed less frequently than average, then the function comes close to that value more often than average. The Second Main Theorem, more difficult than the first one, states roughly that there are relatively few values which the function assumes less often than average.
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