  Since non-compact RCD(0, N) spaces have at least linear volume growth, we
study noncompact RCD(0, N) spaces with linear volume growth in this paper. One
of the main results is that the diameter of level sets of a Busemann function
grow at most linearly on a noncompact RCD(0, N) space satisfying the linear
volume growth condition. Another main result in this paper is a splitting
theorem at the noncompact end for a RCD(0, N) space with strongly minimal
volume growth. These results generalize some theorems on noncompact manifolds
with nonnegative Ricci curvature to non-smooth settings.
