Published online by Cambridge University Press: 21 October 2021
We study the dynamics of the map $f:\mathbb {A}^N\to \mathbb {A}^N$ defined by
$$ \begin{align*} f(\mathbf{X})=A\mathbf{X}^d+\mathbf{b}, \end{align*} $$
for $A\in \operatorname {SL}_N$,
$\mathbf {b}\in \mathbb {A}^N$, and
$d\geq 2$, a class which specializes to the unicritical polynomials when
$N=1$. In the case
$k=\mathbb {C}$ we obtain lower bounds on the sum of Lyapunov exponents of f, and a statement which generalizes the compactness of the Mandelbrot set. Over
$\overline {\mathbb {Q}}$ we obtain estimates on the critical height of f, and over algebraically closed fields we obtain some rigidity results for post-critically finite morphisms of this form.