Application of Tensor Network States to Lattice Field Theories

          @misc{ pirsa_PIRSA:19040109,
            doi = {10.48660/19040109},
            url = {https://pirsa.org/19040109},
            author = {K{\"u}hn, Stefan},
            keywords = {Condensed Matter},
            language = {en},
            title = {Application of Tensor Network States to Lattice Field Theories},
            publisher = {Perimeter Institute},
            year = {2019},
            month = {apr},
            note = {PIRSA:19040109 see, \url{https://pirsa.org}}
          }
          

Abstract

The conventional Euclidean time Monte Carlo approach to Lattice Field Theories faces a major obstacle in the sign problem in certain parameter regimes, such as the presence of a nonzero chemical potential or a topological theta-term. Tensor Network States, a family of ansatzes for the efficient description of quantum many-body states, offer a promising alternative for addressing Lattice Field Theories in the Hamiltonian formulation. In particular, numerical methods based on Tensor Network states do not suffer from the sign problem which makes it possible to study scenarios which are not accessible with standard Monte Carlo methods. In this talk I will present some recent work demonstrating this capability using two (1+1)-dimensional models as a test bed. Studying the O(3) nonlinear sigma model at nonzero chemical potential and the Schwinger model with topological theta-term, I will show how Tensor Networks States accurately describe the low-energy spectrum and that numerical errors can be controlled well enough to make contact with continuum predictions.