Likelihood function for the fundamental domain scale of a cubic torus derived from simulations of a simply-connected Universe, calculated through marginalization (black, filled circles) and profiling (pink, empty circles). The horizontal axis gives the inverse of the length of a side of the fundamental domain, relative to the distance to the last-scattering surface. The vertical lines mark the positions where χ_rec is equal to various characteristic sizes of the fundamental domain, namely the radius of the largest sphere that can be inscribed in the domain, ℛ_i = L/ 2, the smallest sphere in which the domain can be inscribed, , and the intermediate scale .