Lie, Marius Sophus, << lee, MAH ree oos SOH foos >> (1842-1899), was a Norwegian mathematician known for his work in group theory and differential geometry. In group theory, a group is defined as any system of numbers and mathematical operations that obeys certain rules. The numbers and operations can vary from group to group, but the rules are always the same. The rules are simple, and the operations include elementary processes, such as addition and multiplication. However, the mathematics of group theory can be complicated and difficult. Theoretical physicists have used group theory extensively to describe the properties of subatomic particles and the forces that govern the particles. Differential geometry involves the use of calculus to study curves and surfaces. Calculus is the branch of mathematics that deals with changing quantities.
Lie was born on Dec. 17, 1842, in Nordfjordeid, Norway, near Floro. He studied science and mathematics at the University of Christiana in Christiana (now Oslo), Norway. In 1870, he went to Paris, where he worked on group theory with the German mathematician Felix Klein.
When the Franco-Prussian War broke out in 1870, Lie traveled to Italy and Switzerland. In 1872, he returned to Christiana and became a professor of mathematics at the university. There, he developed the theory of groups known as monotonic transformation groups and wrote several important works on differential equations. A differential equation expresses a relationship between a function and its derivative (see Calculus (Derivatives) .
In 1886, Lie went to the University of Leipzig in Germany, where he took over Klein’s chair in mathematics. In 1898, he returned to the University of Christiana, where the Norwegian government had created a chair in the theory of transformation groups. He died in Christiana on Feb. 18, 1899.
