Ernst Leonard Lindelöf (; 7 March 1870 – 4 June 1946) was a

Finnish Finnish may refer to: * Something or someone from, or related to Finland * Culture of Finland * Finnish people or Finns, the primary ethnic group in Finland * Finnish language, the national language of the Finnish people * Finnish cuisine See also ...

mathematician, who made contributions in

real analysis In mathematics, the branch of real analysis studies the behavior of real numbers, sequences and series of real numbers, and real functions. Some particular properties of real-valued sequences and functions that real analysis studies include conv ...

, complex analysis and

topology In mathematics, topology (from the Greek words , and ) is concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing ...

. Lindelöf spaces are named after him. He was the son of mathematician Lorenz Leonard Lindelöf and brother of the

philologist Philology () is the study of language in oral and written historical sources; it is the intersection of textual criticism, literary criticism, history, and linguistics (with especially strong ties to etymology). Philology is also defined as th ...

Biography

Lindelöf studied at the

University of Helsinki The University of Helsinki ( fi, Helsingin yliopisto, sv, Helsingfors universitet, abbreviated UH) is a public research university located in Helsinki, Finland since 1829, but founded in the city of Turku (in Swedish ''Åbo'') in 1640 as the ...

, where he completed his PhD in 1893, became a

docent The title of docent is conferred by some European universities to denote a specific academic appointment within a set structure of academic ranks at or below the full professor rank, similar to a British readership, a French " ''maître de con ...

in 1895 and

professor Professor (commonly abbreviated as Prof.) is an academic rank at universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who professes". Professors ...

of Mathematics in 1903. He was a member of the

Finnish Society of Sciences and Letters The Finnish Society of Sciences and Letters is a Finnish academy for natural sciences, social sciences and humanities. It is known in Latin as Societas Scientiarum Fennica, in Swedish as Finska Vetenskaps-Societeten, and in Finnish as Suomen Tiede ...

. In addition to working in a number of different mathematical domains including complex analysis,

conformal mapping In mathematics, a conformal map is a function that locally preserves angles, but not necessarily lengths. More formally, let U and V be open subsets of \mathbb^n. A function f:U\to V is called conformal (or angle-preserving) at a point u_0\in ...

ordinary differential equation In mathematics, an ordinary differential equation (ODE) is a differential equation whose unknown(s) consists of one (or more) function(s) of one variable and involves the derivatives of those functions. The term ''ordinary'' is used in contrast ...

s and the

gamma function In mathematics, the gamma function (represented by , the capital letter gamma from the Greek alphabet) is one commonly used extension of the factorial function to complex numbers. The gamma function is defined for all complex numbers except ...

, Lindelöf promoted the study of the history of Finnish mathematics. He is known for the

Picard–Lindelöf theorem In mathematics – specifically, in differential equations – the Picard–Lindelöf theorem gives a set of conditions under which an initial value problem has a unique solution. It is also known as Picard's existence theorem, the Cau ...

on differential equations and the

Phragmén–Lindelöf principle In complex analysis, the Phragmén–Lindelöf principle (or method), first formulated by Lars Edvard Phragmén (1863–1937) and Ernst Leonard Lindelöf (1870–1946) in 1908, is a technique which employs an auxiliary, parameterized function to ...

, one of several refinements of the

maximum modulus principle In mathematics, the maximum modulus principle in complex analysis states that if ''f'' is a holomorphic function, then the modulus , ''f'' , cannot exhibit a strict local maximum that is properly within the domain of ''f''. In other words, eit ...

that he proved in

complex function theory Complex analysis, traditionally known as the theory of functions of a complex variable, is the branch of mathematical analysis that investigates functions of complex numbers. It is helpful in many branches of mathematics, including algebraic ...

. He was the PhD supervisor for

Lars Ahlfors Lars Valerian Ahlfors (18 April 1907 – 11 October 1996) was a Finnish mathematician, remembered for his work in the field of Riemann surfaces and his text on complex analysis. Background Ahlfors was born in Helsinki, Finland. His mother, Sie ...

at the

Selected bibliography

*''Le calcul des résidus et ses applications à la théorie des fonctions (Paris, 1905) *''Mémoire sur la théorie des fonctions entières d'ordre fini ("Acta societatis scientiarum fennicae" 31, 1903)'' *With

Lars Edvard Phragmén Lars Edvard Phragmén (2 September 1863 Örebro – 13 March 1937) was a Swedish mathematician. The son of a college professor, he studied at Uppsala then Stockholm, graduating from Uppsala in 1889. He became professor at Stockholm in 1892, afte ...

: "Sur une extension d'un principe classique de l'analyse et sur quelques propriétés des fonctions monogènes dans le voisinage d'un point singulier", in: '' Acta Mathematica'' 31, 1908.

External links

* * * * 1870 births 1946 deaths Scientists from Helsinki 20th-century Finnish mathematicians Topologists 19th-century Finnish mathematicians Academic staff of the University of Helsinki Members of the Royal Society of Sciences in Uppsala {{Europe-mathematician-stub