Georg Friedrich Bernhard Riemann

Bernhard Riemann's ideas concerning geometry of space had a profound effect on the development of modern theoretical physics. He clarified the notion of integral by defining what we now call the Riemann integral. 
Born: 17 Sept 1826 in Breselenz, Hanover (now Germany)
Died: 20 July 1866 in Selasca, Italy 


Introduction
Riemann moved from G?ttingen to Berlin in 1846 to study under Jacobi, Dirichlet and Eisenstein. In 1849 he returned to G?ttingen and his Ph.D. thesis, supervised by Gauss, was submitted in 1851. In his report on the thesis Gauss described Riemann as having a gloriously fertile originality. 
On Gauss's recommendation Riemann was appointed to a post in G?ttingen. Riemann's paper Uber die Hypothesen welche der Geometrie zu Grunde liegen , written in 1854, became a classic of mathematics, and its results were incorporated into Albert Einstein's relativistic theory of gravitation. Gauss's chair at G?ttingen was filled by Dirichlet in 1855 and, after his death, by Riemann. Even at this time he was suffering from tuberculosis and he spent his last years in Italy in an attempt to improve his health. 

Riemann's ideas concerning geometry of space had a profound effect on the development of modern theoretical physics and provided the concepts and methods used later in relativity theory. He was an original thinker and a host of methods, theorems and concepts are named after him. 

The Cauchy-Riemann equations (known before his time) and the concept of a Riemann surface appear in his doctoral thesis. He clarified the notion of integral by defining what we now call the Riemann integral. He is also famed for the still unsolved Riemann hypothesis. 


References

Dictionary of Scientific Biography 
Biography in Encyclopaedia Britannica 
R Dedekind, Biography of Riemann, in H Weber and R Dedekind (eds.), The Collected Works of Riemann (New York, 1953). 
M Monastyrsky, Rieman, Topology and Physics (Boston-Basel, 1987). 
G Schulz, Riemann, in H Wussing and W Arnold, Biographien bedeutender Mathematiker (Berlin, 1983).