What is a $p$-adic Dyson Brownian motion?

We consider the singular numbers of a certain explicit continuous-time Markov jump process on ${\mathrm{G}\mathrm{L}}_N({\mathbb{Q}}_p)$, which we argue gives the closest $p$-adic analogue of multiplicative Dyson Brownian motion. We do so by explicitly classifying the possible dynamics of singular numbers of processes on ${\mathrm{G}\mathrm{L}}_N({\mathbb{Q}}_p)$ satisfying natural properties possessed by Brownian motion on ${\mathrm{G}\mathrm{L}}_N(\mathbb{C})$. Computing the evolution of singular numbers explicitly, we find that the $N$-tuple of singular numbers in decreasing order evolves as a Poisson jump process on ${\mathbb{Z}}^N$, with ordering enforced by reflection off the walls of the positive type $A$ Weyl chamber. This contrasts with – and provides a $p$-adic analogue to – the behavior of classical Dyson Brownian motion, where ordering is enforced by conditioning to avoid the Weyl chamber walls.