Published online by Cambridge University Press: 21 July 2015
We give conditions on the subgroups of the circle to be realized as the subgroups of eigenvalues of minimal Cantor systems belonging to a determined strong orbit equivalence class. Actually, the additive group of continuous eigenvalues   $E(X,T)$  of the minimal Cantor system
 $E(X,T)$  of the minimal Cantor system   $(X,T)$  is a subgroup of the intersection
 $(X,T)$  is a subgroup of the intersection   $I(X,T)$  of all the images of the dimension group by its traces. We show, whenever the infinitesimal subgroup of the dimension group associated with
 $I(X,T)$  of all the images of the dimension group by its traces. We show, whenever the infinitesimal subgroup of the dimension group associated with   $(X,T)$  is trivial, the quotient group
 $(X,T)$  is trivial, the quotient group   $I(X,T)/E(X,T)$  is torsion free. We give examples with non-trivial infinitesimal subgroups where this property fails. We also provide some realization results.
 $I(X,T)/E(X,T)$  is torsion free. We give examples with non-trivial infinitesimal subgroups where this property fails. We also provide some realization results.