The twistor geometry of parabolic structures in rank two

Abstract

Let X be a quasi-projective curve, compactified to (Y, D) with $$X=Y-D$$ . We construct a Deligne–Hitchin twistor space out of moduli spaces of framed $$\lambda $$ -connections of rank 2 over Y with logarithmic singularities and quasi-parabolic structure along D. To do this, one should divide by a Hecke-gauge groupoid. Tame harmonic bundles on X give preferred sections, and the relative tangent bundle along a preferred section has a mixed twistor structure with weights 0, 1, 2. The weight 2 piece corresponds to the deformations of the KMS structure including parabolic weights and the residues of the $$\lambda $$ -connection.