Published online by Cambridge University Press: 12 April 2019
Let be a dominant rational self-map of a smooth projective variety defined over
$\overline{\mathbb{Q}}$. For each point
$P\in X(\overline{\mathbb{Q}})$ whose forward
$f$-orbit is well defined, Silverman introduced the arithmetic degree
$\unicode[STIX]{x1D6FC}_{f}(P)$, which measures the growth rate of the heights of the points
$f^{n}(P)$. Kawaguchi and Silverman conjectured that
$\unicode[STIX]{x1D6FC}_{f}(P)$ is well defined and that, as
$P$ varies, the set of values obtained by
$\unicode[STIX]{x1D6FC}_{f}(P)$ is finite. Based on constructions by Bedford and Kim and by McMullen, we give a counterexample to this conjecture when
$X=\mathbb{P}^{4}$.