First-Principles Simulations of 1+1D Quantum Field Theories at θ=π and Spin Chains

We present a lattice study of a 2-flavor U(1) gauge-Higgs model quantum field theory with a topological term at θ=π. Such studies are prohibitively costly in the standard lattice formulation due to the sign problem. Using a novel discretization of the model, along with an exact lattice dualization, we overcome the sign problem and reliably simulate such systems. Our work provides the first ab initio demonstration that the model is in the spin-chain universality class, and demonstrates the power of the new approach to U(1) gauge theories.