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The Lie algebra structure of HH1(B) for blocks with a normal defect group
Abstract
It is an open question whether the Lie algebra HH1(B) of a block of a finite group algebra kG over an algebraically closed field k of prime characteristic p is simple only if the block is nilpotent with an elementary abelian defect group of order at least $3$. We show this to be the case if B has a normal abelian defect group. Another open question is whether HH1(kSn) is a solvable Lie algebra, where Sn denotes a symmetric group on n letters. We give some general solvability criteria for HH1(B) of blocks B with a normal defect group, and, making use of results of Chuang-Kessar and Chuang-Rouquier, we deduce that if B is a block of a symmetric group algebra with an abelian defect group, then HH1(B) is solvable.
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BibTeX
@misc{linckelmann2026algebra,
title = {{The Lie algebra structure of $\mathrmHH^1(B)$ for blocks with a normal defect group}},
author = {Markus Linckelmann and Jialin Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.32673},
eprint = {2610.32673},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.32673},
}
RIS
TY - UNPB
TI - The Lie algebra structure of HH^1(B) for blocks with a normal defect group
AU - Markus Linckelmann
AU - Jialin Wang
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.32673
UR - https://arxiv.org/abs/2610.32673
AB - It is an open question whether the Lie algebra HH^1(B) of a block of a finite group algebra kG over an algebraically closed field k of prime characteristic p is simple only if the block is nilpotent with an elementary abelian defect group of order at least $3$. We show this to be the case if B has a normal abelian defect group. Another open question is whether HH^1(kS_n) is a solvable Lie algebra, where S_n denotes a symmetric group on n letters. We give some general solvability criteria for HH^1(B) of blocks B with a normal defect group, and, making use of results of Chuang-Kessar and Chuang-Rouquier, we deduce that if B is a block of a symmetric group algebra with an abelian defect group, then HH^1(B) is solvable.
ER -