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Nonlinear Harmonic Bundles

Mao Sheng

TL;DR

The paper introduces nonlinear harmonic bundles as a nonlinear analogue of harmonic bundles in nonabelian Hodge theory by replacing linear fibers with complex manifolds and equipping differentiable bundles with two integrable complex structures connected by a beta-automorphism. It develops a generalized Simpson mechanism, Chern connection theory, and curvature-based harmonicity conditions, anchored in almost connections and almost Higgs fields. It then connects these ideas to relative nonabelian Hodge moduli spaces, proving a rank-one case that ties Gauss-Manin data to Kodaira-Spencer Higgs fields and suggesting a nonlinear Hodge structure on the base. Finally, it establishes a Torelli-type result for abelian varieties, showing that nonlinear Higgs data on moduli spaces captures the isomorphism class of polarized families under strong monodromy, thereby enriching the classical VHS/Torelli framework with nonlinear Higgs dynamics.

Abstract

We generalize the notion of harmonic bundles in nonabelian Hodge theory to the nonlinear setting.

Nonlinear Harmonic Bundles

TL;DR

The paper introduces nonlinear harmonic bundles as a nonlinear analogue of harmonic bundles in nonabelian Hodge theory by replacing linear fibers with complex manifolds and equipping differentiable bundles with two integrable complex structures connected by a beta-automorphism. It develops a generalized Simpson mechanism, Chern connection theory, and curvature-based harmonicity conditions, anchored in almost connections and almost Higgs fields. It then connects these ideas to relative nonabelian Hodge moduli spaces, proving a rank-one case that ties Gauss-Manin data to Kodaira-Spencer Higgs fields and suggesting a nonlinear Hodge structure on the base. Finally, it establishes a Torelli-type result for abelian varieties, showing that nonlinear Higgs data on moduli spaces captures the isomorphism class of polarized families under strong monodromy, thereby enriching the classical VHS/Torelli framework with nonlinear Higgs dynamics.

Abstract

We generalize the notion of harmonic bundles in nonabelian Hodge theory to the nonlinear setting.

Paper Structure

This paper contains 7 sections, 7 theorems, 94 equations.

Key Result

Proposition 2.3

Let $(\alpha, T_{rel})$ be a complex fiber bundle over $S$. Then a complex structure on $(\alpha, T_{rel})$ gives rise to a canonical $\bar{\partial}$-operator on $(\alpha, T_{rel})$. Conversely, a $\bar{\partial}$-operator on $(\alpha, T_{rel})$ gives a canonical almost complex structure on $(\alph

Theorems & Definitions (39)

  • Definition 2.1
  • Definition 2.2
  • Proposition 2.3
  • proof
  • Lemma 2.4
  • proof
  • Definition 2.5
  • Example 2.6
  • Example 2.7
  • Definition 2.8
  • ...and 29 more