Atsuta–Kataoka's shifted Fitting ideal conjecture for class groups

Let R=Z[1/2][G]R=\mathbf{Z}[1/2][G]^-, let ClT(H)\operatorname{Cl}^T(H)^- be the minus part of the TT-smoothed class group, and for each ramified place vv let Av=Z[G/Iv]/(gv)A_v=\mathbf{Z}[G/I_v]/(g_v). With hvh_v^- and FittR[1](Av)\operatorname{Fitt}_R^{[1]}(A_v^-) defined as in the source, and with ΘS,T\Theta_{S_\infty,T} the smoothed Stickelberger element, Atsuta–Kataoka's conjecture. One should have

FittR(ClT(H))=(wSram,HhvFittR[1](Av))ΘS,T.\operatorname{Fitt}_R(\operatorname{Cl}^T(H)^-)=\left(\prod_{w\in S_{\mathrm{ram},H}}h_v^-\operatorname{Fitt}_R^{[1]}(A_v^-)\right)\Theta_{S_\infty,T}.

The conjecture is motivated by shifted Fitting ideals and gives a formula for the Fitting ideal of the class group itself. The source states that the equivariant Tamagawa number conjecture implies it, but does not otherwise resolve it.

Sources & referencesView supporting material

Primary source

Samit Dasgupta and Mahesh Kakde, “On the Brumer-Stark Conjecture and Refinements”, arXiv:2204.09037 (2022).

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