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Preprint, 2026 · Version 1

Motivic Adams isomorphism and tom Dieck splitting in characteristic zero

Mengzhudong Feng

Independent researcher

Manuscript date
First public release

Abstract

We prove a motivic Adams isomorphism for smooth affine linearly reductive groups over fields of characteristic zero. The diagonal of the classifying stack defines an invertible twist. We calculate the twist for finite groups and split tori, and show why it need not be a constant sphere for a split reductive group. We show that geometric fixed points identify each isotropy layer with the lisse motivic category of its Weyl group. Over an algebraically closed field, a normalizer transfer and an isotropy filtration argument give a twisted tom Dieck splitting for G-split spectra, including suspension spectra.

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Please cite the version you used.

Mengzhudong Feng. Motivic Adams isomorphism and tom Dieck splitting in characteristic zero. Preprint, version 1, 2026. GitHub v1 release.

@misc{feng2026motivicadams,
  author = {Feng, Mengzhudong},
  title = {Motivic {Adams} isomorphism and {tom Dieck} splitting in characteristic zero},
  year = {2026},
  note = {Preprint, version 1. Manuscript dated September 27, 2026; released October 8, 2026},
  url = {https://github.com/timfeng-research/motivic-adams-tom-dieck/releases/tag/v1}
}

Version history

Version 1 ·

Initial public release. Manuscript dated September 27, 2026.

GitHub release and source files · PDF v1

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© 2026 Mengzhudong Feng. This paper and its LaTeX manuscript source are licensed under CC BY 4.0.

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