Products of Free Groups in the Unit Group of Integral Group Rings Original Research Article

We classify the nilpotent finite groupsGwhich are such that the unit group image(ZG) of the integral group ringZGhas a subgroup of finite index which is the direct product of noncyclic free groups. It is also shown that nilpotent finite groups having this property can be characterised by means of the Wedderburn decomposition of the rational group algebraQG.