Density conjecture for geometric-origin representations

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Let GG be a linear algebraic group over the complex numbers, let XX be a normal complex variety with base point xx, and write

π=π1(X(C),x),ChG,C□(π)\pi=\pi_1(X(\mathbb C),x),\qquad {\rm Ch}_{G,\mathbb C}^{\Box}(\pi)

for the framed character variety of GG-representations of π\pi. Fix an embedding G↪GL⁡r,CG\hookrightarrow \operatorname{GL}_{r,\mathbb C}. A GG-representation is of geometric origin if, after restriction to a suitable dense open subvariety and semisimplification, its associated linear local system is a direct summand of a local system arising from the higher direct images of a smooth projective morphism.

Density conjecture. The set of GG-representations of geometric origin is Zariski dense in

ChG,C□(π).{\rm Ch}_{G,\mathbb C}^{\Box}(\pi).

This conjecture concerns the density of representations arising from geometry in framed character varieties. The source notes that it holds when GG is abelian, by the torus case of Esnault--Kerz, while Landesman and Litt showed that it is false in this generality because of rank obstructions for geometric local systems with infinite monodromy on certain curves.

References

Primary source

Hélène Esnault and Moritz Kerz, “Local systems with quasi-unipotent monodromy at infinity are dense”, arXiv:2101.00487 (2022).

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