Sidney Martin Webster

{{short description|American mathematician}}

Sidney Martin Webster (born 12 November 1945 in Danville, Illinois) is an American mathematician, specializing in multidimensional complex analysis.{{cite journal|author=Jackson, Allyn|title=Lempert and Webster Receive 2001 Bergman Prize|journal=Notices of the AMS|volume=49|issue=9|pages=998–999|date=October 2001|url=https://www.stat.berkeley.edu/~aldous/Loeve/peres.pdf}}

After military service, Webster attended the University of California, Berkeley as an undergraduate and then as a graduate student, receiving a PhD in 1975 under the supervision of Shiing-Shen Chern with thesis Real hypersurfaces in complex space.{{MathGenealogy|id=13147}} Webster was a faculty member at Princeton University from 1975 to 1980 and at the University of Minnesota from 1980 to 1989. In 1989 he became a full professor at the University of Chicago. He has held visiting positions at the University of Wuppertal, Rice University, and ETH Zurich.

Webster was a Sloan Fellow for the academic year 1979–1980. In 1994 in Zurich he was an invited speaker of the International Congress of Mathematicians.{{cite book|chapter=Geometric and dynamical aspects of real submanifolds of complex spaces|title=Proceedings of the International Congress of Mathematicians, Zürich, 1994|year=1995|pages=917–921|doi=10.1007/978-3-0348-9078-6_84|last1=Webster|first1=Sidney M.|isbn=978-3-0348-9897-3}} In 2001 he received, jointly with László Lempert, the Stefan Bergman Prize from the American Mathematical Society. In 2012 Webster was elected a Fellow of the American Mathematical Society.

In 1977 he proved a significant theorem on biholomorphic mappings between algebraic real hypersurfaces.{{cite journal|author=Webster, S. M.|title=On the mapping problem for algebraic real hypersurfaces|journal=Inventiones Math.|volume=43|pages=53–68|year=1977|doi=10.1007/BF01390203|bibcode=1977InMat..43...53W |s2cid=122533957}} Using his expertise on Chern-Moser invariants, he developed a theory that provides a complete set of invariants for nondegenerate real hypersurfaces under volume-preserving biholomorphic transformations.{{cite journal|author=Webster, S. M.|title=Pseudo-Hermitian structures on a real hypersurface|journal=Journal of Differential Geometry|volume=13|issue=1|year=1978|pages=25–41|doi=10.4310/jdg/1214434345|doi-access=free}} He used the edge-of-the-wedge theorem to prove an extension theorem that generalized a 1974 theorem of Charles Fefferman.{{cite journal|author=Webster, S. M.|title=On the reflection principle in several complex variable|journal=Proc. Amer. Math. Soc.|volume=71|issue=1|date=August 1978|pages=26–28|doi=10.1090/S0002-9939-1978-0477138-4|doi-access=free}}