Convolution-to-sum identities for Mittag-Leffler type functions

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Hauptverfasser: Cvetko, William, Cherkaev, Elena
Format: Preprint
Veröffentlicht: 2026
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author Cvetko, William
Cherkaev, Elena
author_facet Cvetko, William
Cherkaev, Elena
contents Product-to-sum identities for trigonometric functions play a fundamental role in function theory and numerous applications. In this spirit, we present convolution-to-sum identities for Mittag-Leffler type functions. Using a Laplace domain analysis of fractional operators, we identify a family of Mittag-Leffler type functions that encapsulates the eigenfunctions of Riemann-Liouville and Caputo fractional derivatives. We work with two closely-related parameterizations of this class, $R_{α,v}$ and $P_{α,w}$. The convolution of two such functions can be expressed as a series of them. Moreover, if the functions share the same order $α$, the convolution can be reduced to a sum of two $P/R$ functions through a partial-fraction decomposition in the Laplace domain. Furthermore, $R$ and $P$ functions satisfy a generalization of Euler's identity, which expands the scope of the previous result to convolutions of $P/R$ functions whose orders $α_1,α_2$ are related by a rational factor. For $\frac{α_1}{α_2} = \frac{n}{m}$, the resulting sum has $n+m$ terms. The foundational results and methods developed here are illustrated by their application to forced subdiffusion and to a fractionally attenuated wave equation (the Caputo-Wismer-Kelvin, or the fractional Kelvin-Voigt model).
format Preprint
id arxiv_https___arxiv_org_abs_2605_01079
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Convolution-to-sum identities for Mittag-Leffler type functions
Cvetko, William
Cherkaev, Elena
Analysis of PDEs
Mathematical Physics
Product-to-sum identities for trigonometric functions play a fundamental role in function theory and numerous applications. In this spirit, we present convolution-to-sum identities for Mittag-Leffler type functions. Using a Laplace domain analysis of fractional operators, we identify a family of Mittag-Leffler type functions that encapsulates the eigenfunctions of Riemann-Liouville and Caputo fractional derivatives. We work with two closely-related parameterizations of this class, $R_{α,v}$ and $P_{α,w}$. The convolution of two such functions can be expressed as a series of them. Moreover, if the functions share the same order $α$, the convolution can be reduced to a sum of two $P/R$ functions through a partial-fraction decomposition in the Laplace domain. Furthermore, $R$ and $P$ functions satisfy a generalization of Euler's identity, which expands the scope of the previous result to convolutions of $P/R$ functions whose orders $α_1,α_2$ are related by a rational factor. For $\frac{α_1}{α_2} = \frac{n}{m}$, the resulting sum has $n+m$ terms. The foundational results and methods developed here are illustrated by their application to forced subdiffusion and to a fractionally attenuated wave equation (the Caputo-Wismer-Kelvin, or the fractional Kelvin-Voigt model).
title Convolution-to-sum identities for Mittag-Leffler type functions
topic Analysis of PDEs
Mathematical Physics
url https://arxiv.org/abs/2605.01079