Abstract
We prove an elementary formula about the average expansion of certain products of 2 by 2 matrices. This permits us to quickly re-obtain an inequality by M. Herman and a theorem by Dedieu and Shub, both concerning Lyapunov exponents. Indeed, we show that equality holds in Herman’s result. Finally, we give a result about the growth of the spectral radius of products.
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Financial support from Pronex-Dynamical Systems, CNPq 001/2000 and from Faperj is gratefully acknowledged.
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Avila, A., Bochi, J. A formula with some applications to the theory of Lyapunov exponents. Isr. J. Math. 131, 125–137 (2002). https://doi.org/10.1007/BF02785853
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DOI: https://doi.org/10.1007/BF02785853