Linear characters of SL_2 over Dedekind domains
  For an important class of arithmetic Dedekind domains O including the ring of integers of not totally complex number fields, we describe explicitly the group of linear characters of SL_2(O). For this, we determine, for arbitrary Dedekind domains O, the group of linear characters of SL_2(O) whose kernel is a congruence subgroup. 
Hatice Boylan and Nils-Peter Skoruppa
math.NT math.GR