### Abstract

*P(a, z) = γ (a, z)/Γ*

*(a)*and possess early terms that behave like those in an asymptotic expansion. In the case of real variables the function P(

*a,z*) acts as a smoothing factor on the terms of the series. We show how these series representing the Bessel functions of complex argument can be chosen so as to produce rapidly convergent series that possess terms decaying at the geometric rate

*ϑ*

^{k}, where 0 <

*ϑ*< 1 and

*k*is the ordinal number of the series. We give numerical examples with

*ϑ*= 1/2 , 1/3 and 1/4 . The theory is extended to cover the confluent hypergeometric functions

*and*

_{1}F_{1}(a; b; z)*U(a, b, z)*, thereby dealing with many of the special functions arising in mathematical physics.

Original language | English |
---|---|

Pages (from-to) | 84-100 |

Number of pages | 17 |

Journal | Journal of Computational and Applied Mathematics |

Volume | 224 |

Issue number | 1 |

DOIs | |

Publication status | Published - 1 Feb 2009 |

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### Cite this

*Journal of Computational and Applied Mathematics*,

*224*(1), 84-100. https://doi.org/10.1016/j.cam.2008.04.025

}

*Journal of Computational and Applied Mathematics*, vol. 224, no. 1, pp. 84-100. https://doi.org/10.1016/j.cam.2008.04.025

**High-precision evaluation of the Bessel functions via Hadamard series.** / Paris, Richard B.

Research output: Contribution to journal › Article

TY - JOUR

T1 - High-precision evaluation of the Bessel functions via Hadamard series

AU - Paris, Richard B.

PY - 2009/2/1

Y1 - 2009/2/1

N2 - We present a method of high-precision calculation of the Bessel functions using Hadamard series. Such series are absolutely convergent expansions involving the normalised incomplete gamma function P(a, z) = γ (a, z)/Γ(a) and possess early terms that behave like those in an asymptotic expansion. In the case of real variables the function P(a,z) acts as a smoothing factor on the terms of the series. We show how these series representing the Bessel functions of complex argument can be chosen so as to produce rapidly convergent series that possess terms decaying at the geometric rate ϑk , where 0 < ϑ < 1 and k is the ordinal number of the series. We give numerical examples with ϑ = 1/2 , 1/3 and 1/4 . The theory is extended to cover the confluent hypergeometric functions 1 F 1 (a; b; z) and U(a, b, z), thereby dealing with many of the special functions arising in mathematical physics.

AB - We present a method of high-precision calculation of the Bessel functions using Hadamard series. Such series are absolutely convergent expansions involving the normalised incomplete gamma function P(a, z) = γ (a, z)/Γ(a) and possess early terms that behave like those in an asymptotic expansion. In the case of real variables the function P(a,z) acts as a smoothing factor on the terms of the series. We show how these series representing the Bessel functions of complex argument can be chosen so as to produce rapidly convergent series that possess terms decaying at the geometric rate ϑk , where 0 < ϑ < 1 and k is the ordinal number of the series. We give numerical examples with ϑ = 1/2 , 1/3 and 1/4 . The theory is extended to cover the confluent hypergeometric functions 1 F 1 (a; b; z) and U(a, b, z), thereby dealing with many of the special functions arising in mathematical physics.

U2 - 10.1016/j.cam.2008.04.025

DO - 10.1016/j.cam.2008.04.025

M3 - Article

VL - 224

SP - 84

EP - 100

JO - Journal of Computational and Applied Mathematics

JF - Journal of Computational and Applied Mathematics

SN - 0377-0427

IS - 1

ER -