The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them

The Bessel function of the first kind <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>J</mi><mi>N</mi></msub><mfenced separators="" open="(&q...

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Main Author: Jack C. Straton
Format: Article
Language:English
Published: MDPI AG 2024-02-01
Series:Axioms
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Online Access:https://www.mdpi.com/2075-1680/13/2/134
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author Jack C. Straton
author_facet Jack C. Straton
author_sort Jack C. Straton
collection DOAJ
description The Bessel function of the first kind <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>J</mi><mi>N</mi></msub><mfenced separators="" open="(" close=")"><mi>k</mi><mi>x</mi></mfenced></mrow></semantics></math></inline-formula> is expanded in a Fourier–Legendre series, as is the modified Bessel function of the first kind <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>I</mi><mi>N</mi></msub><mfenced separators="" open="(" close=")"><mi>k</mi><mi>x</mi></mfenced></mrow></semantics></math></inline-formula>. The purpose of these expansions in Legendre polynomials was not an attempt to rival established <i>numerical</i> methods for calculating Bessel functions but to provide a form for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>J</mi><mi>N</mi></msub><mfenced separators="" open="(" close=")"><mi>k</mi><mi>x</mi></mfenced></mrow></semantics></math></inline-formula> useful for <i>analytical</i> work in the area of strong laser fields, where analytical integration over scattering angles is essential. Despite their primary purpose, one can easily truncate the series at 21 terms to provide 33-digit accuracy that matches the IEEE extended precision in some compilers. The analytical theme is furthered by showing that infinite series of like-powered contributors (involving <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mo> </mo><mspace width="-0.166667em"></mspace></mrow><mn>1</mn></msub><msub><mi>F</mi><mn>2</mn></msub></mrow></semantics></math></inline-formula> hypergeometric functions) extracted from the Fourier–Legendre series may be summed, having values that are inverse powers of the eight primes <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mo>/</mo><mfenced separators="" open="(" close=")"><msup><mn>2</mn><mi>i</mi></msup><msup><mn>3</mn><mi>j</mi></msup><msup><mn>5</mn><mi>k</mi></msup><msup><mn>7</mn><mi>l</mi></msup><msup><mn>11</mn><mi>m</mi></msup><msup><mn>13</mn><mi>n</mi></msup><msup><mn>17</mn><mi>o</mi></msup><msup><mn>19</mn><mi>p</mi></msup></mfenced></mrow></semantics></math></inline-formula> multiplying powers of the coefficient <i>k</i>.
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spelling doaj.art-ec494ca71b45423399ef5cb18ba6cab92024-02-23T15:07:31ZengMDPI AGAxioms2075-16802024-02-0113213410.3390/axioms13020134The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from ThemJack C. Straton0Department of Physics, Portland State University, Portland, OR 97207-0751, USAThe Bessel function of the first kind <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>J</mi><mi>N</mi></msub><mfenced separators="" open="(" close=")"><mi>k</mi><mi>x</mi></mfenced></mrow></semantics></math></inline-formula> is expanded in a Fourier–Legendre series, as is the modified Bessel function of the first kind <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>I</mi><mi>N</mi></msub><mfenced separators="" open="(" close=")"><mi>k</mi><mi>x</mi></mfenced></mrow></semantics></math></inline-formula>. The purpose of these expansions in Legendre polynomials was not an attempt to rival established <i>numerical</i> methods for calculating Bessel functions but to provide a form for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>J</mi><mi>N</mi></msub><mfenced separators="" open="(" close=")"><mi>k</mi><mi>x</mi></mfenced></mrow></semantics></math></inline-formula> useful for <i>analytical</i> work in the area of strong laser fields, where analytical integration over scattering angles is essential. Despite their primary purpose, one can easily truncate the series at 21 terms to provide 33-digit accuracy that matches the IEEE extended precision in some compilers. The analytical theme is furthered by showing that infinite series of like-powered contributors (involving <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mo> </mo><mspace width="-0.166667em"></mspace></mrow><mn>1</mn></msub><msub><mi>F</mi><mn>2</mn></msub></mrow></semantics></math></inline-formula> hypergeometric functions) extracted from the Fourier–Legendre series may be summed, having values that are inverse powers of the eight primes <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mo>/</mo><mfenced separators="" open="(" close=")"><msup><mn>2</mn><mi>i</mi></msup><msup><mn>3</mn><mi>j</mi></msup><msup><mn>5</mn><mi>k</mi></msup><msup><mn>7</mn><mi>l</mi></msup><msup><mn>11</mn><mi>m</mi></msup><msup><mn>13</mn><mi>n</mi></msup><msup><mn>17</mn><mi>o</mi></msup><msup><mn>19</mn><mi>p</mi></msup></mfenced></mrow></semantics></math></inline-formula> multiplying powers of the coefficient <i>k</i>.https://www.mdpi.com/2075-1680/13/2/134Bessel functionsFourier–Legendre seriesLaplace seriesgeneralized hypergeometric functionspolynomial approximationscomputational methods
spellingShingle Jack C. Straton
The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them
Axioms
Bessel functions
Fourier–Legendre series
Laplace series
generalized hypergeometric functions
polynomial approximations
computational methods
title The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them
title_full The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them
title_fullStr The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them
title_full_unstemmed The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them
title_short The Fourier–Legendre Series of Bessel Functions of the First Kind and the Summed Series Involving <sub>1</sub><i>F</i><sub>2</sub> Hypergeometric Functions That Arise from Them
title_sort fourier legendre series of bessel functions of the first kind and the summed series involving sub 1 sub i f i sub 2 sub hypergeometric functions that arise from them
topic Bessel functions
Fourier–Legendre series
Laplace series
generalized hypergeometric functions
polynomial approximations
computational methods
url https://www.mdpi.com/2075-1680/13/2/134
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