# Stephen M. Gersten

Stephen M. Gersten (born 2 December 1940) was an American mathematician, specializing in finitely presented groups and their geometric properties.[1]

Gersten graduated in 1961 with an AB from Princeton University[1] and in 1965 with a PhD from Trinity College, Cambridge. His doctoral thesis was Class Groups of Supplemented Algebras written under the supervision of John R. Stallings.[2] In the late 1960s and early 1970s he taught at Rice University. In 1972–1973 he was a visiting scholar at the Institute for Advanced Study.[3] In 1973 he became a professor at the University of Illinois at Urbana–Champaign.[1] In 1974 he was an Invited Speaker at the International Congress of Mathematicians in Vancouver.[4] At the University of Utah he became a professor in 1975 and is now semi-retired there.[1] His PhD students include Roger C. Alperin and Edward W. Formanek.[2]

Gersten's conjecture has motivated considerable research.[5]

## Gersten's theorem

If φ is an automorphism of a finitely generated free group F then { x : xF and φ(x) ${\displaystyle =}$ x } is finitely generated.[6][7]