Stability under transverse perturbations

Determine whether the self-accelerating positive–negative active-mass binary is stable against sideways perturbations by evolving configurations that are not exactly head-on.

Background

All simulations in the paper release the two soliton stars on a head-on trajectory. The reported stability of the separation, acceleration, and common motion therefore applies only to this symmetric one-dimensional configuration. Stability with respect to transverse disturbances is explicitly left unresolved.