The characteristic-cycle pullback conjecture for log-clean ramification

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Suppose that XX is purely of dimension dd and that DD has simple normal crossings. Let I′⊂II'\subset I be a subset containing IT,FI_{\mathrm{T},\mathcal{F}}, and let

D′=⋃i∈I′Di.D'=\bigcup_{i\in I'}D_i.

Assume that the ramification of F\mathcal{F} is log⁡\log-D′D'-clean along DD, and that the inverse image

τD′−1(SD′log⁡(j!F))⊂T∗X\tau_{D'}^{-1}\bigl(S_{D'}^{\log}(j_{!}\mathcal{F})\bigr)\subset T^*X

of the log⁡\log-D′D'-singular support SD′log⁡(j!F)⊂T∗X(log⁡D′)S_{D'}^{\log}(j_{!}\mathcal{F})\subset T^*X(\log D') by the canonical morphism τD′\tau_{D'} is of dimension dd. Characteristic-cycle pullback conjecture. Then

CC(j!F)=τD′!CCD′log⁡(j!F)CC(j_{!}\mathcal{F})=\tau_{D'}^{!}CC_{D'}^{\log}(j_{!}\mathcal{F})

in Zd(τD′−1(SD′log⁡(j!F)))Z_d\bigl(\tau_{D'}^{-1}(S_{D'}^{\log}(j_{!}\mathcal{F}))\bigr), where τD′!\tau_{D'}^{!} is the indicated Gysin map. This conjecture predicts that, under the stated cleanliness and dimension hypotheses, the ordinary characteristic cycle is obtained from the logarithmic characteristic cycle by pullback; its status is not established by the supplied text.

References

Primary source

Yuri Yatagawa, “Singular support and Characteristic cycle of a rank one sheaf in codimension two”, arXiv:2206.02989 (2022).

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