Continuum limits of matrix product states

We determine which translationally invariant matrix product states have a continuum limit, that is, which can be considered as discretized versions of states defined in the continuum. To do this, we analyze a fine-graining renormalization procedure in real space, characterize the set of limiting states of its flow, and find that it strictly contains the set of continuous matrix product states. We also analyze which states have a continuum limit after a finite number of coarse-graining renormalization steps. We give several examples of states with and without the different kinds of continuum limits.