SL₂ — The negative solutions

Abstract

In the previous chapter, we dealt with solvable groups and the methods came from abelian groups. In this chapter, we deal with $S{L_2}({\mathcal{O}_S})$ where $\mathcal{O}$ is the ring of integers in an algebraic number field and S is any set of places containing all the archimedean ones. The methods here will be very different from those of the previous chapter.