An upper limit to the electric dipole moment of the neutron from lattice QCD

A linear increase with the volume of the topological susceptibility can signal spontaneous breaking of parity P and time inversion T, due to a nonzero vacuum expectation value of the topological charge Q. Such a breaking would produce a nonzero electric dipole moment of the neutron, dn. An upper limit to dn is derived from numerical simulations at increasing volumes.