Topological susceptibility, scale setting and universality from $Sp(N_c)$ gauge theories

In this contribution, we report on our study of the properties of the Wilson flow and on the calculation of the topological susceptibility of $Sp(N_c)$ gauge theories for $N_c=2,4,6,8$. The Wilson flow is shown to scale according to the quadratic Casimir operator of the gauge group, as was already observed for $SU(N_c)$, and the commonly used scales $t_0$ and $w_0$ are obtained for a large interval of the inverse coupling for each probed value of $N_c$. The continuum limit of the topological susceptibility is computed and we conjecture that it scales with the dimension of the group. The lattice measurements performed in the $SU(N_c)$ Yang-Mills theories by several independent collaborations allow us to test this conjecture and to obtain a universal large-$N_c$ limit of the rescaled topological susceptibility.