%0 Journal Article %T Nilpotent extensions of blocks %A Lluis Puig %J Mathematics %D 2010 %I arXiv %X There are normal sub-blocks of nilpotent blocks which are NOT nilpotent or, equivalently, nilpotent extensions of non-nilpotent blocks. In this paper we determine the source algebra structure of the non-nilpotent blocks involved in these situations. Actually, we introduce a new type of blocks - called the inertial blocks - which include the nilpotent blocks and is closed by taking normal sub-blocks. %U http://arxiv.org/abs/1004.1613v1