Johann Peter Gustav Lejeune Dirichlet (
February 13, 1805 –
May 5, 1859) was a
German mathematician credited with the modern "formal" definition of a
function.
His family hailed from the town of
Richelette in
Belgium, from which his surname "Lejeune Dirichlet" ("",
French for "the young chap from Richelette") was derived. That was also where his grandfather lived.
Dirichlet was born in
Düren, where his father was the
postmaster. He was educated in
Germany, and then
France, where he learnt from many of the most renowned mathematicians of the day. He also learned from
Georg Ohm. His first paper was on
Fermat's last theorem comprised of a partial proof for the case <math>n = 5</math>, which was completed by
Adrien-Marie Legendre, who was one of the referees. Dirichlet also completed his own proof almost at the same time; he later also produced a full proof for the case <math>n = 14</math>.
In 1831, he married
Rebecca Henriette Mendelssohn Bartholdy, who came from a distinguished family of converts from Judaism to Christianity; she was a granddaughter of the philosopher
Moses Mendelssohn, daughter of
Abraham Mendelssohn Bartholdy and a sister of the composers
Felix Mendelssohn Bartholdy and
Fanny Mendelssohn.
Ferdinand Eisenstein, Leopold Kronecker, and
Rudolf Lipschitz were his students. After his death, Dirichlet's lectures and other results in
number theory were collected, edited and published by his friend and fellow mathematician
Richard Dedekind under the title (
Lectures on Number Theory).
