  Recent results have demonstrated that samplers constructed with flow-based
generative models are a promising new approach for configuration generation in
lattice field theory. In this paper, we present a set of methods to construct
flow models for targets with multiple separated modes (i.e. theories with
multiple vacua). We demonstrate the application of these methods to modeling
two-dimensional real scalar field theory in its symmetry-broken phase. In this
context we investigate the performance of different flow-based sampling
algorithms, including a composite sampling algorithm where flow-based proposals
are occasionally augmented by applying updates using traditional algorithms
like HMC.
