English

Universal deformation rings and dihedral 2-groups

Representation Theory 2009-01-24 v2 Group Theory

Abstract

Let kk be an algebraically closed field of characteristic 2, and let WW be the ring of infinite Witt vectors over kk. Suppose DD is a dihedral 2-group. We prove that the universal deformation ring R(D,V)R(D,V) of an endo-trivial kDkD-module VV is always isomorphic to W[Z/2×Z/2]W[\mathbb{Z}/2\times\mathbb{Z}/2]. As a consequence we obtain a similar result for modules VV with stable endomorphism ring kk belonging to an arbitrary nilpotent block with defect group DD. This confirms for such VV conjectures on the ring structure of the universal deformation ring of VV which had previously been shown for VV belonging to cyclic blocks or to blocks with Klein four defect groups.

Keywords

Cite

@article{arxiv.0705.0834,
  title  = {Universal deformation rings and dihedral 2-groups},
  author = {Frauke Bleher},
  journal= {arXiv preprint arXiv:0705.0834},
  year   = {2009}
}
R2 v1 2026-06-21T08:25:27.349Z