Hain's conjecture on NMHS structures on relative Malcev completions

Let XX be a pointed space with fundamental group π1(X,x)\pi_1(X,x), let V\mathcal V be a variation of Hodge structure with fibre Vx\mathcal V_x and polarization ,\langle\cdot,\cdot\rangle, and let

ρ:π1(X,x)Aut(Vx,,)\rho:\pi_1(X,x)\to \operatorname{Aut}(\mathcal V_x,\langle\cdot,\cdot\rangle)

be its monodromy representation. Let SS be the Zariski closure of the image of ρ\rho, and let G\mathscr G be the relative Malcev completion of π1(X,x)\pi_1(X,x) with respect to the induced representation into SS.

Hain's conjecture. The relative completion G\mathscr G should carry a nonabelian mixed Hodge structure in general. This structure should be a quotient of π1hodge(X,x)\pi_1^{\mathrm{hodge}}(X,x).

Hain proved this assertion when the monodromy representation has Zariski-dense image in the relevant reductive algebraic group. The conjectural extension concerns the case where the target is the Zariski closure of the monodromy image.

Sources & referencesView supporting material

Primary source

Donu Arapura, “The Hodge theoretic fundamental group and its cohomology”, arXiv:0902.4252 (2009).

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