English

Lie algebroid connection and Harder-Narasimhan reduction

Algebraic Geometry 2026-01-27 v1

Abstract

Take a holomorphic Lie algebroid (V,ϕ)(V,\, \phi) on a compact connected Riemann surface XX such that the anchor map ϕ\phi is not surjective. Let PP be a parabolic subgroup of a complex reductive affine algebraic group GG and EPEGE_P\, \subset\, E_G a holomorphic reduction of structure group, to PP, of a holomorphic principal GG--bundle EGE_G on XX. We prove that EPE_P admits a holomorphic Lie algebroid connection for (V,ϕ)(V,\,\phi) if the reduction EPE_P is infinitesimally rigid. If EPE_P is the Harder--Narasimhan reduction of EGE_G, then it is shown that EPE_P admits a holomorphic Lie algebroid connection for (V,ϕ)(V,\,\phi). In particular, for any point x0Xx_0\,\in\, X, the Harder--Narasimhan reduction EPE_P admits a logarithmic connection that is nonsingular on the complement X{x0}X\setminus\{x_0\}.

Keywords

Cite

@article{arxiv.2601.18169,
  title  = {Lie algebroid connection and Harder-Narasimhan reduction},
  author = {Ashima Bansal and Indranil Biswas and Pradip Kumar},
  journal= {arXiv preprint arXiv:2601.18169},
  year   = {2026}
}

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11 pages