Niels Erik Nørlund

Niels Erik Nørlund (1885 to 1981) was a Danish mathematician and astronomer who worked in the theory of difference equations. He was born in Slagelse, studied mathematics and astronomy at the University of Copenhagen from 1903 and worked as an assistant at the Astronomical Observatory there. He won a gold medal in 1907 for an essay on continued fractions and defended his doctoral thesis on linear differential equations in 1910. In 1912 he took a new chair of mathematics at the University of Lund in Sweden, where he concentrated on difference equations, factorial series and interpolation series. His work on summability gave the method known as Nørlund summation. He was elected to the Danish Academy of Sciences in 1916. His sister Margrethe married the physicist Niels Bohr, and his brother Poul became an archaeologist.