Scattering phase shift determinations from a two-scalar field theory

A field theory involving two interacting scalar fields, previously studied by Rummukainen and Gottlieb, is revisited. Our study is not restricted to the limit of large quartic couplings, and a Symanzik-improved action is used so that continuum dispersion relations work well. The Metropolis method, combined with a local microcanonical updating algorithm, is employed in our Monte Carlo calculations. Isotropic lattices ranging from ${16}^3\times 48$ to $53^3 \times 48$ are used, and scattering phase shifts are determined using a L"uscher analysis with multiple partial waves.