Essential minimum and obstruction degrees of translates of subtori

Abstract

We study the obstruction degrees of translates of sub-tori of multiplicative tori and we show how they are connected to lower bounds for the essential minimum of these varieties. In particular, we combine our computations with results of A. Schinzel and of F. Amoroso - R. Dvornicich, that we thus extend to translates of sub-tori defined over CM fields. This shows that the essential minimum of these varieties have a geometric behavior similar to that of varieties which are not translates of sub-tori. We also refine and extend to translates of sub-tori a lower bound obtained by D. Bertrand in connexion with relations of multiplicative dependence of algebraic points. Finaly, we prove that in the functional case the conjectural lower bound for the essential minimum of sub-varieties of multiplicative tori is true and its proof is elementary.