1. The Kobayashi–Royden metric on punctured spheres
- Author
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Junqing Qian and Gunhee Cho
- Subjects
Rational number ,Pure mathematics ,Applied Mathematics ,General Mathematics ,010102 general mathematics ,01 natural sciences ,Exponential function ,Bell polynomials ,010101 applied mathematics ,Metric (mathematics) ,Backslash ,SPHERES ,0101 mathematics ,Asymptotic expansion ,Mathematics - Abstract
This paper gives an explicit formula of the asymptotic expansion of the Kobayashi–Royden metric on the punctured sphere ℂ ℙ 1 ∖ { 0 , 1 , ∞ } {\mathbb{CP}^{1}\setminus\{0,1,\infty\}} in terms of the exponential Bell polynomials. We prove a local quantitative version of the Little Picard’s Theorem as an application of the asymptotic expansion. Furthermore, the approach in the paper leads to the interesting consequence that the coefficients in the asymptotic expansion are rational numbers. Furthermore, the explicit formula of the metric and the conclusion regarding the coefficients apply to more general cases of ℂ ℙ 1 ∖ { a 1 , … , a n } {\mathbb{CP}^{1}\setminus\{a_{1},\ldots,a_{n}\}} , n ≥ 3 {n\geq 3} , as well, and the metric on ℂ ℙ 1 ∖ { 0 , 1 3 , - 1 6 ± 3 6 i } {\mathbb{CP}^{1}\setminus\{0,\frac{1}{3},-\frac{1}{6}\pm\frac{\sqrt{3}}{6}i\}} will be given as a concrete example of our results.
- Published
- 2020