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arXiv 0812.2578math.AG
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二重有理正态曲线

Doubling rational normal curves

Roberto Notari, Ignacio Ojeda, Maria Luisa Spreafico

摘要:

本文研究了有理正态曲线上的二重结构。在回顾\cite{fer}中描述的光滑曲线上支撑的二重结构的一般构造后,我们将其专门化为有理正态曲线上的二重结构。对于每一个双曲线结构,我们关联一个整数三元组$ (2r,g,n) $,其中$ r $是支撑度,$ n \geq r $是包含双曲线的射影空间的维数,$ g $是双曲线的算术亏格。我们还计算一些数值不变量的构造曲线,我们表明,家庭的双重结构与一个给定的三重$ (2r,g,n) $是不可约的。进一步证明了$ (2r,r+1,r) $和$ (2r,1,2r-1) $族中的一般双曲线是算术Gorenstein曲线.最后证明了含亏格为$ g \leq -2 $的双二次曲线的轨迹的闭包构成相应Hilbert格式的不可约分量,且一般双二次曲线是该分量的光滑点.证明了任意亏格的$ \mathbb{P}^3 $中的一般双二次曲线是相应Hilbert格式的光滑点。

英文摘要:

In this paper, we study double structures supported on rational normal curves. After recalling the general construction of double structures supported on a smooth curve described in \cite{fer}, we specialize it to double structures on rational normal curves. To every double structure we associate a triple of integers $ (2r,g,n) $ where $ r $ is the degree of the support, $ n \geq r $ is the dimension of the projective space containing the double curve, and $ g $ is the arithmetic genus of the double curve. We compute also some numerical invariants of the constructed curves, and we show that the family of double structures with a given triple $ (2r,g,n) $ is irreducible. Furthermore, we prove that the general double curve in the families associated to $ (2r,r+1,r) $ and $ (2r,1,2r-1) $ is arithmetically Gorenstein. Finally, we prove that the closure of the locus containing double conics of genus $ g \leq -2 $ form an irreducible component of the corresponding Hilbert scheme, and that the general double conic is a smooth point of that component. Moreover, we prove that the general double conic in $ \mathbb{P}^3 $ of arbitrary genus is a smooth point of the corresponding Hilbert scheme.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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