Charting the space of ground states with matrix product states
In this talk I will use matrix product states (MPS) to study topological families of gapped ground states in one spatial dimension. To such families I will describe how to associate a gerbe, a mathematical structure which generalizes the line bundle associated to gapped ground states in 0d. Nontriviality of the gerbe represents an obstruction to representing the family of ground states with an MPS tensor that is continuous everywhere over parameter space. I will illustrate these constructions using an exactly solvable topological family which exhibits the key physics in a simple manner.