There and Back Again: Revisiting the Failure of Concatenation in Mittag-Leffler Functions

TL;DR

This paper rigorously proves that the Mittag-Leffler function only satisfies the semigroup property in fractional calculus when specific parameters are met, highlighting the nonlocal nature of fractional differential equations.

Contribution

It provides a rigorous analytical proof clarifying when the Mittag-Leffler function exhibits the semigroup property, addressing a gap in the understanding of fractional dynamics.

Findings

Semigroup property holds only if α=1 or λ=0.

Establishes a precise criterion for Mittag-Leffler functions and semigroup compatibility.

Highlights the nonlocality of fractional-order differential equations.

Abstract

The function $t \mapsto E_{\alpha}(\lambda t^\alpha)$ is widely regarded as the fractional analogue of the exponential function, yet its algebraic properties remain poorly understood. In particular, standard references lack a rigorous proof of the failure of the semigroup property. In this work, we fill this gap by providing an analytical proof that the semigroup property holds if and only if either $\alpha = 1$ or $\lambda = 0$. Our result establishes a precise criterion for when Mittag-Leffler dynamics are compatible with semigroup evolution, thereby emphasizing the intrinsic nonlocality of fractional-order differential equations.