Kronecker Conjugacy of Polynomials

Let f, g ∈ Z[X] be non-constant polynomials with integral coefficients. In 1968 H. Davenport raised the question as to when the value sets f(Z) and g(Z) are the same modulo all but finitely many primes. The main progress until now is M. Fried’s result that f and g then differ by a linear substitution, provided that f is functionally indecomposable. We extend this result to polynomials f of composition length 2. Also, we study the analog when Z is replaced by the integers of a number field. The above number theoretic property translates to an equivalent property of subgroups of a finite group, known as Kronecker conjugacy, a weakening of conjugacy which has been studied by various authors under different assumptions and in other contexts. We also give a simplified and strengthened version of the Galois theoretic translation to finite groups.