Convergent expansions of the incomplete gamma functions in terms of elementary functions

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Date
2017Version
Acceso abierto / Sarbide irekia
Type
Artículo / Artikulua
Version
Versión aceptada / Onetsi den bertsioa
Impact
|
10.1142/S0219530517500099
Abstract
We consider the incomplete gamma function γ(a,z) for Ra>0 and z∈C. We derive several convergent expansions of z−aγ(a,z) in terms of exponentials and rational functions of z that hold uniformly in z with Rz bounded from below. These expansions, multiplied by ez, are expansions of ezz−aγ(a,z) uniformly convergent in z with Rz bounded from above. The expansions are accompanied by realistic error bou ...
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We consider the incomplete gamma function γ(a,z) for Ra>0 and z∈C. We derive several convergent expansions of z−aγ(a,z) in terms of exponentials and rational functions of z that hold uniformly in z with Rz bounded from below. These expansions, multiplied by ez, are expansions of ezz−aγ(a,z) uniformly convergent in z with Rz bounded from above. The expansions are accompanied by realistic error bounds. [--]
Subject
Incomplete gamma functions,
Convergent expansions,
Uniform expansions
Publisher
World Scientific Publishing
Published in
Analysis and Applications, vol. 16, no. 03
Departament
Universidad Pública de Navarra. Departamento de Ingeniería Matemática e Informática /
Nafarroako Unibertsitate Publikoa. Matematika eta Informatika Ingeniaritza Saila /
Universidad Pública de Navarra/Nafarroako Unibertsitate Publikoa. Institute for Advanced Materials and Mathematics - INAMAT2
Publisher version
Sponsorship
This research was supported by the Spanish Ministry of Economía y Competitividad, projects
MTM2014-53178-P and TEC2013-45585-C2-1-R. The Universidad Pública de Navarra is
acknowledged by its financial support.