Transcendence tests for Mahler functions

Abstract:

We give two tests for transcendence of Mahler functions. For our first, we introduce the notion of the eigenvalue $\lambda _F$ of a Mahler function $F(z)$ and develop a quick test for the transcendence of $F(z)$ over $\mathbb {C}(z)$, which is determined by the value of the eigenvalue $\lambda _F$. While our first test is quick and applicable for a large class of functions, our second test, while a bit slower than our first, is universal; it depends on the rank of a certain Hankel matrix determined by the initial coefficients of $F(z)$. We note that these are the first transcendence tests for Mahler functions of arbitrary degree. Several examples and applications are given.