Equivariant generating hypotheses for finite groups
Abstract
We prove that no nontrivial finite group G satisfies the equivariant generating hypothesis of Bohmann, even when all RO(H)-graded homotopy groups are tested for every subgroup H≤ G. For each G, we construct ghosts on finite G-spectra with arbitrarily long nonzero composition powers. We also prove that the homotopy-module functors are nonfull and construct non-equivalent finite G-spectra with isomorphic full homotopy modules. A central ingredient of our proof is the natural ghost operation Ψ=(p−[Cp/e])(1−g) on Cp-spectra. Motivated by Ma--Xu's examples in the motivic settings, we apply this operation to both a two-cell complex and products of complex projective spaces with cyclic permutation action, which produces arbitrarily long nonzero ghost powers. We also construct a ghost on an explicit four-cell complex that is detected in the derived category over the group ring.
Related
BibTeX
@misc{ma2026equivariant,
title = {{Equivariant generating hypotheses for finite groups}},
author = {Sihao Ma and XiaoLin Danny Shi and Zhouli Xu and Shangjie Zhang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.24390},
eprint = {2609.24390},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24390},
}
RIS
TY - UNPB
TI - Equivariant generating hypotheses for finite groups
AU - Sihao Ma
AU - XiaoLin Danny Shi
AU - Zhouli Xu
AU - Shangjie Zhang
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2609.24390
UR - https://arxiv.org/abs/2609.24390
AB - We prove that no nontrivial finite group G satisfies the equivariant generating hypothesis of Bohmann, even when all RO(H)-graded homotopy groups are tested for every subgroup H≤ G. For each G, we construct ghosts on finite G-spectra with arbitrarily long nonzero composition powers. We also prove that the homotopy-module functors are nonfull and construct non-equivalent finite G-spectra with isomorphic full homotopy modules. A central ingredient of our proof is the natural ghost operation Ψ=(p−[C_p/e])(1−g) on C_p-spectra. Motivated by Ma--Xu's examples in the motivic settings, we apply this operation to both a two-cell complex and products of complex projective spaces with cyclic permutation action, which produces arbitrarily long nonzero ghost powers. We also construct a ghost on an explicit four-cell complex that is detected in the derived category over the group ring.
ER -