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© The London Mathematical Society 2006
THE NUMBER OF DISTINCT EIGENVALUES OF ELEMENTS IN FINITE LINEAR GROUPS
School of Mathematics, University of East Anglia Norwich NR4 7TJ, United Kingdom a.zalesskii{at}uea.ac.uk
Received 4 July 2005. Revision received 9 November 2005.
Let G be a finite (non-abelian) irreducible linear subgroup over the complex numbers, and let g be an element of G of prime order p. Suppose that g does not belong to a proper normal subgroup of G. We show that the number of distinct eigenvalues of g can only be p,p 1,p2,(p + 1)/2 or (p1)/2. Moreover, we provide a full classification of such groups G provided that g has at most p2 distinct eigenvalues.