P=W for resolutions of character varieties

Let CC be a smooth projective curve and GG a reductive group. Let MDol(C,G)M_{\mathrm{Dol}}(C,G) and MB(C,G)M_{\mathrm{B}}(C,G) be the untwisted Dolbeault and Betti moduli spaces, with non-abelian Hodge correspondence Ψ\Psi. The conjecture asks for resolutions of singularities

fDol ⁣:M~Dol(C,G)MDol(C,G),fB ⁣:M~B(C,G)MB(C,G),f_{\mathrm{Dol}}\colon \widetilde{M}_{\mathrm{Dol}}(C,G)\to M_{\mathrm{Dol}}(C,G),\qquad f_{\mathrm{B}}\colon \widetilde{M}_{\mathrm{B}}(C,G)\to M_{\mathrm{B}}(C,G),

together with a diffeomorphism Ψ~ ⁣:M~Dol(C,G)M~B(C,G)\widetilde{\Psi}\colon\widetilde{M}_{\mathrm{Dol}}(C,G)\to\widetilde{M}_{\mathrm{B}}(C,G) lifting Ψ\Psi and making the induced cohomological square commute.

P=W for resolution. The lift satisfies, for every kk,

PkH(M~Dol(C,G),Q)=Ψ~W2kH(M~B(C,G),Q).P_kH^*(\widetilde{M}_{\mathrm{Dol}}(C,G),\mathbb{Q})=\widetilde{\Psi}^*W_{2k}H^*(\widetilde{M}_{\mathrm{B}}(C,G),\mathbb{Q}).

This is a strong form of PI=WI. The source states that it was proved for character varieties admitting a symplectic resolution, but explains that it fails when no symplectic resolution exists; the unrestricted formulation is therefore refuted.

Sources & referencesView supporting material

Primary source

Mirko Mauri, “Intersection cohomology of rank two character varieties of surface groups”, arXiv:2101.04628 (2021).

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