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

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Let R=Z[1/2][G]−R=\mathbf{Z}[1/2][G]^-, let Cl⁡T(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 hv−h_v^- and Fitt⁡R[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

Fitt⁡R(Cl⁡T(H)−)=(∏w∈Sram,Hhv−Fitt⁡R[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.

References

Primary source

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

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