Differential Galois theory in Strasbourg

Becker’s conjecture on Mahler functions

5 sept. 2019, 15:00

1h

Salle séminaire (Strasbourg)

Orateur

Frédéric Chyzak

Description

In 1994, Becker conjectured that if $F(z)$ is a $k$-regular power series, then there exists a $k$-regular rational function $R(z)$ such that $F(z)/R(z)$ satisfies a Mahler-type functional equation with polynomial coefficients where the initial coefficient satisfies $a_0(z)=1$. In this work, we prove Becker’s conjecture in the best possible form; we show that the rational function $R(z)$ can be taken to be a polynomial $z^{\gamma }Q(z)$ for some explicit non-negative integer $\gamma$ and such that $1/Q(z)$ is $k$-regular. (This is joint work with Jason P. Bell, Michael Coons, and Philippe Dumas.)