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arXiv · 1906.12023

Evaluation of Abramowitz functions in the right half of the complex plane

Zydrunas Gimbutas·Shidong Jiang·Li-Shi Luo
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Abstract

A numerical scheme is developed for the evaluation of Abramowitz functions $J_n$ in the right half of the complex plane. For $n=-1,\, \ldots,\, 2$, the scheme utilizes series expansions for $|z|<1$ and asymptotic expansions for $|z|>R$ with $R$ determined by the required precision, and modified Laurent series expansions which are precomputed via a least squares procedure to approximate $J_n$ accurately and efficiently on each sub-region in the intermediate region $1\le |z| \le R$. For $n>2$, $J_n$ is evaluated via a recurrence relation. The scheme achieves nearly machine precision for $n=-1, \ldots, 2$, with the cost about four times of evaluating a complex exponential per function evaluation.

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Zydrunas Gimbutas, Shidong Jiang, Li-Shi Luo. 2019-06-28. Evaluation of Abramowitz functions in the right half of the complex plane. https://doi.org/10.1016/j.jcp.2019.109169

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