The Iwasawa decomposition and intermediate subgroups of the Steinberg groups over the field of fractions of a principal ideal ring. (Q1042887)

The Iwasawa decomposition for the Steinberg groups of types \(^2A_{2l-1}\), \(^2D_l\), \(^2E_6\), \(^3D_4\) over the field of fractions \(K\) of a principal ideal ring \(D\) is used to describe the subgroups between the Steinberg groups over the rings \(D\) and \(K\) under some restrictions on the ring \(D\). The answer involves the subrings of \(K\) containing \(D\).