A family of Thue equations involving powers of units of the simplest cubic fields

Abstract

E. Thomas was one of the first to solve an infinite family of Thue equations, when he considered the forms $F_n(X,Y)=X^3-(n-1)X^{2}Y-(n+2)X{Y}^2-Y^3$ and the family of equations $F_n(X,Y)=\pm 1$, $n\in \mathbf{N}$. This family is associated to the family of the simplest cubic fields $\mathbf{Q}(\lambda )$ of D. Shanks, $\lambda$ being a root of $F_n(X,1)$. We introduce in this family a second parameter by replacing the roots of the minimal polynomial $F_n(X,1)$ of $\lambda$ by the $a$-th powers of the roots and we effectively solve the family of Thue equations that we obtain and which depends now on the two parameters $n$ and $a$.

Expanded version (31p) of a paper to appear in the Journal de Théorie des Nombres de Bordeaux