The multiplicative tom Dieck splitting conjecture for structure Xi

From papers

Let GG be a compact Lie group, let KK range over the closed subgroups of GG, and write WK=NG(K)/KW_K=N_G(K)/K for the Weyl group and \AdWK\Ad_{W_K} for its adjoint representation. Let RR be an augmented EE_{\infty} algebra, let RΦKR^{\Phi K} denote its geometric KK-fixed points, and let jEΞj_{\mathcal{E}}^{\Xi} denote the comparison from the putative multiplicative structure Ξ\Xi to the operadic structure. The notation RΦK^S\AdWKR^{\Phi K}\mathbin{\widehat\otimes}S^{\Ad_{W_K}} denotes the dimension-shifted based tensor, and ()WKEWK(-)\otimes_{W_K}EW_K denotes the Weyl-group orbit construction.

Multiplicative tom Dieck splitting conjecture. There exists a multiplicative structure Ξ\Xi such that Ξ\Xi-algebras are in particular GG-EE_{\infty} algebras and, in the augmented or nonunital setting, admit dimension-shifting multiplicative transfers for all closed subgroups. For every augmented EE_{\infty} algebra RR, these transfers induce an equivalence

(K)<G$RΦK^S\AdWK$WKEWK,,((jEΞ)R)ΦG.\coprod_{(K)<G} \$R^{\Phi K} \mathbin{\widehat\otimes} S^{\Ad_{W_K}}\$\otimes_{W_K}EW_K \xrightarrow{\\,\sim\\,} ((j_{\mathcal{E}}^{\Xi})_{*}R)^{\Phi G}.

The conjecture proposes a multiplicative enhancement of the additive tom Dieck splitting, extending the observed dimension-shifting transfer structure beyond ordinary operadic algebras. Its status is unknown: the existence of Ξ\Xi and the asserted splitting remain to be established.

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Sources & referencesView supporting material

Primary source

Andrew J. Blumberg and Michael A. Mandell, “A multiplicative version of the tom Dieck splitting”, arXiv:2505.02721 (2025).

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