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Journal of the American Mathematical Society

ISSN 1088-6834(online) ISSN 0894-0347(print)



Word maps and Waring type problems

Authors: Michael Larsen and Aner Shalev
Journal: J. Amer. Math. Soc. 22 (2009), 437-466
MSC (2000): Primary 20D06, 20G40; Secondary 14G15
Published electronically: September 12, 2008
MathSciNet review: 2476780
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Abstract | References | Similar Articles | Additional Information


Waring’s classical problem deals with expressing every natural number as a sum of $g(k)$ $k$th powers. Recently there has been considerable interest in similar questions for nonabelian groups and simple groups in particular. Here the $k$th power word is replaced by an arbitrary group word $w \ne 1$, and the goal is to express group elements as short products of values of $w$.

We give a best possible and somewhat surprising solution for this Waring type problem for various finite simple groups, showing that a product of length two suffices to express all elements. We also show that the set of values of $w$ is very large, improving various results obtained so far.

Along the way we also obtain new results of independent interest on character values and class squares in symmetric groups.

Our methods involve algebraic geometry, representation theory, probabilistic arguments, as well as results from analytic number theory, including three primes theorems (approximating Goldbach’s Conjecture).

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Additional Information

Michael Larsen
Affiliation: Department of Mathematics, Indiana University, Bloomington, Indiana 47405
MR Author ID: 293592

Aner Shalev
Affiliation: Einstein Institute of Mathematics, Hebrew University, Givat Ram, Jerusalem 91904, Israel
MR Author ID: 228986
ORCID: 0000-0001-9428-2958

Keywords: Word maps, finite simple groups, Waring’s problem
Received by editor(s): February 1, 2007
Published electronically: September 12, 2008
Additional Notes: The first author was partially supported by NSF grant DMS-0354772
The second author was partially supported by an Israel Science Foundation Grant.
Both authors were partially supported by a Bi-National Science Foundation United States-Israel Grant.
Article copyright: © Copyright 2008 American Mathematical Society