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On the diophantine equation \(| ax^n-by^n|=1\). (English) Zbl 0892.11041

In this paper the authors show that the equation of the title with \(b \geq a\) and \(n\geq 3\) has at most one integer solution \((x,y)\in\mathbb{N}\times\mathbb{N}\) with the possible exceptions of values of \(a, b\) and \(n\) such that \[ b=a+1,\quad 2\leq a\leq \min\{0.3 n,83\},\quad 17 \leq n \leq 347. \] This is achieved in a novel way by combining results on linear forms in logarithms with results on Padé approximations to hypergeometric functions. All the relevant computations are explained in great detail, including all the necessary number field data such as the fundamental units and various ideal generators. This data is required for a variety of number fields of degree up to \(13\). Four different techniques for reducing the upper bounds, derived from estimates on linear forms in logarithms, are given and contrasted. These are the classical method of Tzanakis and de Weger, using simultaneous linear forms, the method of Bilu and Hanrot using two-dimensional lattices and a new method which is a combination of the others.

MSC:

11Y50 Computer solution of Diophantine equations
11D41 Higher degree equations; Fermat’s equation
Full Text: DOI

References:

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