The two-dimensional O(3) model at nonzero density: from dual lattice simulations to repulsive bosons

Understand

We discuss the thermodynamics of the O(3) nonlinear sigma model in 1+1 dimensions at nonzero chemical potential (equivalent to a magnetic field).

• In its conventional field theory representation the model suffers from a sign problem.
• By dualizing the lattice model we present, for the first time, nonzero density data of an asymptotically free theory with dynamical mass-gap.
• We find a quantum phase transition at zero temperature where as a function of the chemical potential the density assumes a nonzero value.