Autoduality conjecture for the ring stack sW{}^{s}W

Let QQ be the quotient of the Witt vector ring stack WW by its formal subgroup W^\hat W, let TF(Q)T_F(Q) denote the associated Tate module, and let sW{}^{s}W be the extension of WW by TF(Q)T_F(Q) appearing above. For Rp-NilpR\in\operatorname{p-Nilp}, write

sWR:=sW×SpecR{}^{s}W_R:={}^{s}W\times\operatorname{Spec} R

and let αRExt(sWR,Zp(1)R)\alpha_R\in\operatorname{Ext}({}^{s}W_R,\mathbb{Z}_p(1)_R) be the base change of the extension class αExt(sW,Zp(1))\alpha\in\operatorname{Ext}({}^{s}W,\mathbb{Z}_p(1)). Let

fR:sW(R)Ext(sWR,Zp(1)R)f_R:{}^{s}W(R)\to\operatorname{Ext}({}^{s}W_R,\mathbb{Z}_p(1)_R)

be the unique W(R)W(R)-linear map satisfying fR(1)=αRf_R(1)=\alpha_R. Autoduality conjecture. The map fRf_R is an isomorphism.

This conjecture asserts that the ring stack sW{}^{s}W is autodual under the relevant Ext pairing, uniformly after base change to every pp-nilpotent ring. The supplied text does not state whether the conjecture is known or open.

Sources & referencesView supporting material

Primary source

Vladimir Drinfeld, “Ring stacks conjecturally related to the stacks BT_n^G,μ”, arXiv:2510.04958 (2026).

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