A Lower Bound for the Height of a Rational Function at S-unit Points

• Autores: Pietro Corvaja, Umberto Zannier
• Localización: Monatshefte für mathematik, ISSN 0026-9255, Vol. 144, Nº 3, 2005, págs. 203-224
• Idioma: inglés
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• Resumen

  • Let a,b be given, multiplicatively independent positive integers and let >0. In a recent paper jointly with Y. Bugeaud we proved the upper bound exp(n) for g.c.d.(an¿1, bn¿1); shortly afterwards we generalized this to the estimate g.c.d.(u¿1,v¿1)u,v) for multiplicatively independent S-units u,vZ. In a subsequent analysis of those results it turned out that a perhaps better formulation of them may be obtained in terms of the language of heights of algebraic numbers. In fact, the purposes of the present paper are: to generalize the upper bound for the g.c.d. to pairs of rational functions other than {u¿1,v¿1} and to extend the results to the realm of algebraic numbers, giving at the same time a new formulation of the bounds in terms of height functions and algebraic subgroups of Gm2.