The large N limit of the topological susceptibility of Yang-Mills gauge theory

We present a precise computation of the topological susceptibility χYM of SU(N) Yang-Mills theory in the large N limit. The computation is done on the lattice, using high-statistics Monte Carlo simulations with N =3;4;5;6 and three different lattice spacings. Two major improvements make it possible to go to finer lattice spacing and larger N compared to previous works. First, the topological charge is implemented through the gradient flow definition; and second, open boundary conditions in the time direction are employed in order to avoid the freezing of the topological charge. The results allow us to extrapolate the dimensionless quantity t02 χYM to the continuum and large N limits with confidence. The accuracy of the final result represents a new quality in the verification of large N scaling.