Piers Bohl

Piers Bohl (born 11 Oktoberjul / October 23 1865greg Walk in, .. † December 25, 1921 in Riga ) was a Livonian mathematician who worked on almost periodic functions, celestial mechanics and differential equations.

Life and work

Bohl was born the son of a Baltic German merchant in Livonia and went into Fellin on the Livonian ritterschaftliche Landesgymnasium. From 1884 he studied mathematics at Dorpat (amongst others with the astronomer Anders Lindstedt ) where in 1886 he received a gold medal for his work on " Theory and Application of the invariants of linear differential equations " and in 1887, made ​​his candidate 's degree. He then worked as a teacher. In 1893 he received his doctorate in Dorpat ( Master's thesis, "On the representation of functions of variables by trigonometric series with more of a variables proportional arguments" ) and taught from 1895 at the Baltic Polytechnic Institute in Riga, at that time under Russian rule ( he also taught in Russian). In 1900 he qualified as a professor in Dorpat in Adolf Kneser (doctoral dissertation: About some differential equations in mechanics applicable general character ), and became a professor in Riga. During the First World War, the university was evacuated to Moscow, where Bohl spent three grueling years for him. In the short period of Latvia's independence in 1919 Bohl returned to Riga back to the university, but died of a stroke two years later.

Bohl examined the first (in his master's dissertation of 1893) quasi-periodic functions, which were rediscovered in 1903 by French astronomer Ernest Esclangon ( He coined the name) and were later studied extensively by Harald Bohr, generalized almost periodic functions. Bohl examined this in the context of celestial mechanics problems ( perturbation theory ). Bohl also examined in his dissertation differential equations of mechanical systems at their equilibrium points with topological methods ( in connection to Henri Poincaré and Adolf Kneser ) and proved this in 1904 a form of Brouwer's fixed point theorem for continuous mapping of the sphere to itself ( seven years before the work of Luitzen Egbertus January Brouwer 1911 ). He also led early studies on the equal distribution of numbers mod 1 by the sense of the later work of Hermann Weyl, also in the context of celestial mechanics.

Bohl was also a strong chess player, who competed with the Baltic chess champion Karl Behting Riga against other European chess clubs ( such as that of Berlin). He found, for example, a " Riga variation " of the Spanish Opening.

Bohl never married.

Writings

• "On the motion of a mechanical system near its position of equilibrium ", Journal Pure Applied Mathematics, Bd.127, 1904, p.179 -276 ( anticipation of Brouwer's fixed point theorem )