Dirichlet (Peter Gustav Lejeune, 1805 ~ 1859) is a German mathematician. He made outstanding contributions to number theory, mathematical analysis and mathematical physics, and was one of the founders of analytic number theory. /kloc-0 was born in Dylan in February, 805, and/kloc-0 died in gottingen on May 5, 859. He was taught by physicist g.s. ohm in middle school; 1822 to 1826 studied in Paris and was deeply influenced by J.B.J Fourier. After returning to China, he taught in breslau University, Berlin Military Academy and Berlin University for 27 years, which had a great influence on the development of German mathematics. 1839 was a professor at the University of Berlin, and 1855 took over the position of Professor C.F. Gauss at the University of G? ttingen.

In analysis, he was one of the first mathematicians who advocated strict methods. 1837, he put forward the modern viewpoint that function is the corresponding relationship between x and y.

In number theory, he is the disseminator and disseminator of Gauss thought. 1833, Dirichlet wrote "Lecture Notes on Number Theory", which clearly explained Gauss's epoch-making work "Arithmetic Research" and made his thoughts widely spread. 1837, he constructed Dirichlet series. From 1838 to 1839, he got the formula to determine the class number of quadratic forms. In 1846, the pigeon hole principle is used. The structure of Abel group of unit number in algebraic number field is expounded.

In mathematical physics, he has done important work on topics such as gravity produced by ellipsoid, motion of ball in incompressible fluid and general stability derived from the stability of solar system. 1850 published an article on potential theory and discussed the famous first boundary value problem, which is now called Dirichlet problem.