||It has been suggested that this article be merged into Lang's theorem. (Discuss) Proposed since March 2014.|
In mathematics, the Lang–Steinberg theorem, introduced by Lang (1956) for the special case of the Frobenius endomorphism F and by Steinberg (1968) in general, gives conditions for the Lang map g → g−1F(g) of an endomorphism F of an algebraic group to be surjective.
Suppose that F is an endomorphism of an algebraic group G. The Lang map is the map from G to G taking g to g−1F(g).
The Lang–Steinberg theorem states that if F is surjective and has a finite number of fixed points, and G is a connected affine algebraic group over an algebraically closed field, then the Lang map is surjective.
- Lang, Serge (1956), "Algebraic groups over finite fields", American Journal of Mathematics 78: 555–563, ISSN 0002-9327, MR 0086367
- Steinberg, Robert (1968), Endomorphisms of linear algebraic groups, Memoirs of the American Mathematical Society, No. 80, Providence, R.I.: American Mathematical Society, MR 0230728