English

Structure of blocks with normal defect and abelian $p'$ inertial quotient

Representation Theory 2022-01-28 v1

Abstract

Let kk be an algebraically closed field of prime characteristic pp. Let kGekGe be a block of a group algebra of a finite group GG, with normal defect group PP and abelian pp' inertial quotient LL. Then we show that kGekGe is a matrix algebra over a quantised version of the group algebra of a semidirect product of PP with a certain subgroup of LL. To do this, we first examine the associated graded algebra, using a Jennings--Quillen style theorem. As an example, we calculate the associated graded of the basic algebra of the non-principal block in the case of a semidirect product of an extraspecial pp-group PP of exponent pp and order p3p^3 with a quaternion group of order eight with the centre acting trivially. In the case p=3p=3 we give explicit generators and relations for the basic algebra as a quantised version of kPkP. As a second example, we give explicit generators and relations in the case of a group of shape 21+4:31+22^{1+4}:3^{1+2} in characteristic two.

Keywords

Cite

@article{arxiv.2201.11715,
  title  = {Structure of blocks with normal defect and abelian $p'$ inertial quotient},
  author = {David Benson and Radha Kessar and Markus Linckelmann},
  journal= {arXiv preprint arXiv:2201.11715},
  year   = {2022}
}

Comments

21 pages