Johan Ludwig Jensen

Johan Jensen

Johan Ludwig William Valdemar Jensen (born May 8, 1859 in Nakskov , † March 5, 1925 in Copenhagen ) was a Danish mathematician .

Jensen grew up partly in northern Sweden, where his father was an estate manager, and went to school in Copenhagen. There he studied natural sciences and mathematics at the Polytechnic from 1876. While still a student, he published his first work on mathematics. He then worked as an engineer at the Bell Telephone Company and later the Copenhagen Telephone Company , but in his spare time continued researching mathematics and published mathematical papers. In 1890 he became the head of the technical department of the Copenhagen Telephone Company, for which he worked until his retirement in 1924. His training in higher mathematics was largely self-paced; he never received a doctorate and did not acquire any higher degrees in mathematics.

Johan Ludwig Jensen's best-known mathematical result is certainly the Jensen's inequality for convex functions, named after him .

Jensen's formula is also named after him , which establishes a connection for a meromorphic function between the integral of over a circle and the zero and pole positions from within the circle. This formula is of fundamental importance in the value distribution theory established by Nevanlinna . It was part of Jensen's attempt to prove the Riemann Hypothesis . Further work concerned the gamma function and infinite rows. ${\displaystyle f}$ ${\displaystyle \log |f|}$ ${\displaystyle f}$

From 1892 to 1903 he was President of the Danish Mathematical Society .

Web links

• John J. O'Connor, Edmund F. Robertson :  Johan Ludwig Jensen. In: MacTutor History of Mathematics archive .

Individual evidence

1. ↑ JLWV Jensen: Sur les fonctions convexes et les inégalités entre les valeurs moyennes. In: Acta Mathematica. 30, 1906, pp. 175-193.
2. ↑ JLWV Jensen: Sur un nouvel et important théorème de la théorie des fonctions. In: Acta Mathematica. 22, 1899, pp. 359-364.