The genuine equivariant K-theory block decomposition conjecture

Let GG be a finite group, let pp be a prime, and let qq denote an unramified extension parameter. Write KG,q\mathbf{K}_{G,q} for the corresponding unramified genuine equivariant K-theory spectrum, and Kq[ZG(c)]\mathbf{K}_q[\mathit{Z}_G(c)] for the K-theory group-ring spectrum of the centralizer ZG(c)\mathit{Z}_G(c) of an element cGc\in G. The notation ()ω(-)^\omega denotes compact objects and ()ft(-)^{\mathit{ft}} denotes the finite-type subcategory.

Genuine equivariant K-theory block decomposition conjecture. There is an equivalence of stable \infty-categories

LMod(KG,q)ωcLMod(Kq[ZG(c)])ft,\mathrm{LMod}(\mathbf{K}_{G,q})^\omega \cong \bigoplus_c \mathrm{LMod}(\mathbf{K}_q[\mathit{Z}_G(c)])^{\mathit{ft}},

where the sum is over representatives for conjugacy classes of elements cGc\in G of order prime to pp, and ZG(c)\mathit{Z}_G(c) denotes the centralizer of cc.

The conjecture proposes that the additional blocks appearing in genuine equivariant K-theory are not essentially new, and is closely related to a question raised by Akhil Mathew. It concerns the Bredon, rather than Borel, equivariant theory; the supplied source does not state whether it has been resolved.

Sources & referencesView supporting material

Primary source

David Treumann, “Representations of finite groups on modules over K-theory (with an appendix by Akhil Mathew)”, arXiv:1503.02477 (2015).

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