English

On semi-finite vector bundles with connection over Kahler manifolds

Algebraic Geometry 2025-08-26 v1

Abstract

Let XX be a compact connected K\"ahler manifold. We consider the category CEC(X)\mathcal{C}^\mathrm{EC}(X) of flat holomorphic connections (E,E)(E,\, \nabla^E) over XX satisfying the condition that the underlying holomorphic vector bundle EE admits a filtration of holomorphic subbundles preserved by the connection E\nabla^E such that the monodromy of the induced connection on each successive quotient has finite image. The category CEC(X)\mathcal{C}^\mathrm{EC}(X), equipped with the neutral fiber functor that sends any object (E,E)(E,\, \nabla^E) to the fiber Ex0E_{x_0}, where x0Xx_0\, \in\, X is a fixed point, defines a neutral Tannakian category over C\mathbb{C}. Let ϖEC(X,x0)\varpi^{\mathrm{EC}}(X,\, x_0) denote the affine group scheme corresponding to this neutral Tannakian category CEC(X)\mathcal{C}^\mathrm{EC}(X). Let πEN(X,x0)\pi^{\mathrm{EN}}(X,\, x_0) be an extension of the Nori fundamental group scheme over C\mathbb{C}. We show that πEN(X,x0)\pi^{\mathrm{EN}}(X,\, x_0) is a closed subgroup scheme of ϖEC(X,x0)\varpi^{\mathrm{EC}}(X,\, x_0). Finally, we discuss an example illustrating that if XX is not K\"ahler, then the natural homomorphism πEN(X,x0)ϖEC(X,x0)\pi^{\mathrm{EN}}(X,\, x_0)\, \longrightarrow\, \varpi^{\mathrm{EC}}(X,\, x_0) might fail to be an embedding.

Keywords

Cite

@article{arxiv.2508.17048,
  title  = {On semi-finite vector bundles with connection over Kahler manifolds},
  author = {Sanjay Amrutiya and Indranil Biswas},
  journal= {arXiv preprint arXiv:2508.17048},
  year   = {2025}
}

Comments

Final version