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Main Author: Sokal, Alan D.
Format: Preprint
Published: 2002
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Online Access:https://arxiv.org/abs/math/0212035
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author Sokal, Alan D.
author_facet Sokal, Alan D.
contents I present and analyze a quadratically convergent algorithm for computing the infinite product \prod_{n=1}^\infty (1 - tx^n) for arbitrary complex t and x satisfying |x| < 1, based on the identity \prod_{n=1}^\infty (1 - tx^n) = \sum_{m=0}^\infty {(-t)^m x^{m(m+1)/2} \over (1-x)(1-x^2) ... (1-x^m)} due to Euler. The efficiency of the algorithm deteriorates as |x| \uparrow 1, but much more slowly than in previous algorithms. The key lemma is a two-sided bound on the Dedekind eta function at pure imaginary argument, η(iy), that is sharp at the two endpoints y=0,\infty and is accurate to within 9.1% over the entire interval 0 < y < \infty.
format Preprint
id arxiv_https___arxiv_org_abs_math_0212035
institution arXiv
publishDate 2002
record_format arxiv
spellingShingle Numerical Computation of \prod_{n=1}^\infty (1 - tx^n)
Sokal, Alan D.
Numerical Analysis
33F05 (Primary) 05A30, 11F20, 11P82, 33D99, 65D20, 82B23 (Secondary)
I present and analyze a quadratically convergent algorithm for computing the infinite product \prod_{n=1}^\infty (1 - tx^n) for arbitrary complex t and x satisfying |x| < 1, based on the identity \prod_{n=1}^\infty (1 - tx^n) = \sum_{m=0}^\infty {(-t)^m x^{m(m+1)/2} \over (1-x)(1-x^2) ... (1-x^m)} due to Euler. The efficiency of the algorithm deteriorates as |x| \uparrow 1, but much more slowly than in previous algorithms. The key lemma is a two-sided bound on the Dedekind eta function at pure imaginary argument, η(iy), that is sharp at the two endpoints y=0,\infty and is accurate to within 9.1% over the entire interval 0 < y < \infty.
title Numerical Computation of \prod_{n=1}^\infty (1 - tx^n)
topic Numerical Analysis
33F05 (Primary) 05A30, 11F20, 11P82, 33D99, 65D20, 82B23 (Secondary)
url https://arxiv.org/abs/math/0212035