Semiclassical Limits of Strongly Parabolic Higgs Bundles and Hyperpolygon Spaces
Lynn Heller, Sebastian Heller, Claudio Meneses
TL;DR
This work analyzes the semiclassical degeneration of the Hitchin hyperkähler metric for strongly parabolic $\mathfrak{sl}(2,\mathbb{C})$-Higgs bundles on the $n$-punctured sphere as parabolic weights are scaled to zero ($t\to0$). It constructs real holomorphic sections (twistor lines) of the parabolic Deligne–Hitchin moduli space by solving a loop-group monodromy problem, linking them to the twistor lines of hyperpolygon spaces via a precise limiting process. It proves that, after rescaling by $t^{-1}$, the Hitchin metric on energy-bounded subsets of $\mathcal{M}_{\mathrm{Higgs}}(t\alpha)$ converges to the hyperkähler metric on the hyperpolygon space $\mathcal{X}_\alpha$, providing a finite-dimensional model for the degeneration of the infinite-dimensional hyperkähler reduction. Moreover, higher-order corrections in the semiclassical regime are expressed explicitly through iterated integrals of logarithmic differentials on the punctured sphere, enabling systematic computation of metric expansions. Overall, the hyperpolygon spaces emerge as the natural finite-dimensional limits governing the degeneration of Hitchin moduli spaces, with twistor theory giving a cohesive, computable framework for the asymptotics.
Abstract
We investigate the Hitchin hyperkähler metric on the moduli space of strongly parabolic $\mathfrak{sl}(2,\C)$-Higgs bundles on the $n$-punctured Riemann sphere and its degeneration obtained by scaling the parabolic weights $tα$ as $t\to0$. Using the parabolic Deligne--Hitchin moduli space, we show that twistor lines of hyperpolygon spaces arise as limiting initial data for twistor lines at small weights, and we construct the corresponding real-analytic families of $λ$-connections. On suitably shrinking regions of the moduli space, the rescaled Hitchin metric converges, in the semiclassical limit, to the hyperkähler metric on the hyperpolygon space $\mathcal X_α$, which thus serves as the natural finite-dimensional model for the degeneration of the infinite-dimensional hyperkähler reduction. Moreover, higher-order corrections of the Hitchin metric in this semiclassical regime can be expressed explicitly in terms of iterated integrals of logarithmic differentials on the punctured sphere.
