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arXiv 1605.08656math.CVmath.DG
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切片正则函数的扭量解释

Twistor interpretation of slice regular functions

Amedeo Altavilla

摘要:

给定一个切片正则函数$f:Ω\subset\mathbb{H}\to \mathbb{H}$,利用$Ω\cap\mathbb{R}\neq \emptyset$,可以将其提升到$\mathbb{S}^4\simeq \mathbb{H}\cup \{\infty\}$的扭量空间$\mathbb{CP}^{3}$中的曲面(参见~ \cite{gensalsto})。在本文中,我们表明,同样的结果是真实的,如果一个删除的功能$f$域上的假设$Ω\cap\mathbb{R}\neq \emptyset$。此外,我们发现,如果曲面$\mathcal{S}\subset\mathbb{CP}^{3}$包含切片正则函数的扭量提升的图像,则$\mathcal{S}$必须由线来划分。从这些结果出发,我们发现所有的投影类代数曲面的程度3 $\mathbb{CP}^{3}$,包含提升的切片定期功能。此外,我们还扩展和进一步探讨了所谓的扭量变换,即$\mathbb{G}r_2(\mathbb{C}^4)$中的一条曲线,给定一个切片正则函数,它返回其提升进行的线的排列。通过切片正则函数的扭量提升和扭量变换的显式表达式,我们展示了一组切片正则函数,其扭量变换描述了$\mathbb{G}r_2(\mathbb{C}^4)$中的一条有理线,显示了未在$\mathbb{R}$上定义的切片正则函数的作用。最后,我们研究了一个特殊的切片正则函数的扭量提升的实数上没有定义。这个例子显示了我们的方法的有效性,并提出了一些问题。

英文摘要:

Given a slice regular function $f:Ω\subset\mathbb{H}\to \mathbb{H}$, with $Ω\cap\mathbb{R}\neq \emptyset$, it is possible to lift it to a surface in the twistor space $\mathbb{CP}^{3}$ of $\mathbb{S}^4\simeq \mathbb{H}\cup \{\infty\}$ (see~\cite{gensalsto}). In this paper we show that the same result is true if one removes the hypothesis $Ω\cap\mathbb{R}\neq \emptyset$ on the domain of the function $f$. Moreover we find that if a surface $\mathcal{S}\subset\mathbb{CP}^{3}$ contains the image of the twistor lift of a slice regular function, then $\mathcal{S}$ has to be ruled by lines. Starting from these results we find all the projective classes of algebraic surfaces up to degree 3 in $\mathbb{CP}^{3}$ that contain the lift of a slice regular function. In addition we extend and further explore the so-called twistor transform, that is a curve in $\mathbb{G}r_2(\mathbb{C}^4)$ which, given a slice regular function, returns the arrangement of lines whose lift carries on. With the explicit expression of the twistor lift and of the twistor transform of a slice regular function we exhibit the set of slice regular functions whose twistor transform describes a rational line inside $\mathbb{G}r_2(\mathbb{C}^4)$, showing the role of slice regular functions not defined on $\mathbb{R}$. At the end we study the twistor lift of a particular slice regular function not defined over the reals. This example shows the effectiveness of our approach and opens some questions.

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