On a theorem of Narasimhan and Ramanan on deformations

Let $X$ be a smooth projective curve genus $G$ (as elaborated in \ref{main1}), over an algebraically closed field $k$ of arbitrary characteristics. Let $\cH$ {\em be a tamely ramified absolutely simple, simply connected connected group scheme (see \eqref{quasisplitcase})}. Let $\cM$ denote the moduli stack $\cM_X(\cH)$ of $\cH$-torsors on $X$ and $\cM^{^s}$ be the open substack of {\em stable torsors}. Using the theory of parahoric torsors and Parahoric-correspondences, we describe the cohomology groups $\text{H}^i\left(\cM^{^s}, \cT_{_{\cM}}\right), i = 0,1,2$ and $\text{H}^i\left(\cM^{^s}, Ω_{_{\cM}}\right), i = 0,1,2$ in terms of the curve $X$. The classical results of Narasimhan and Ramanan are derived as a consequence.

Publication Details

Journal
arXiv (Cornell University)
Published
2025-06-21
Primary Topic
Algebraic Geometry and Number Theory
Type
article
Field-Weighted Citation Impact
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article

On a theorem of Narasimhan and Ramanan on deformations

arXiv (Cornell University)
Algebraic Geometry and Number Theory
article

On a theorem of Narasimhan and Ramanan on deformations

article en

Abstract

Let $X$ be a smooth projective curve genus $G$ (as elaborated in \ref{main1}), over an algebraically closed field $k$ of arbitrary characteristics. Let $\cH$ {\em be a tamely ramified absolutely simple, simply connected connected group scheme (see \eqref{quasisplitcase})}. Let $\cM$ denote the moduli stack $\cM_X(\cH)$ of $\cH$-torsors on $X$ and $\cM^{^s}$ be the open substack of {\em stable torsors}. Using the theory of parahoric torsors and Parahoric-correspondences, we describe the cohomology groups $\text{H}^i\left(\cM^{^s}, \cT_{_{\cM}}\right), i = 0,1,2$ and $\text{H}^i\left(\cM^{^s}, Ω_{_{\cM}}\right), i = 0,1,2$ in terms of the curve $X$. The classical results of Narasimhan and Ramanan are derived as a consequence.

arXiv (Cornell University)
Openalex Percentile: Top 42%
Algebraic Geometry and Number Theory
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On a theorem of Narasimhan and Ramanan on deformations · arXiv (Cornell University) (2025) | TGRS Research Map | TGRS