Stellar streams form when galaxies or globular clusters are tidally disrupted by the gravitational field of a larger galaxy. Tidal streams are observed in the halo of the Milky Way --- for example the Sagittarius, Orphan, or Palomar 5 streams --- and are also found around external galaxies. Tidal streams in the halo of the Milky Way are powerful tracers of the underlying shape and distribution of mass in the Galactic dark matter halo.
Understanding how tidal streams form and evolve will allow us to measure detailed properties of the Milky Way's gravitational field at large distances and therefore place constraints on the behavior of dark matter on galactic scales.
Dynamical chaos occurs when a system displays extreme sensitivity to initial conditions --- two orbits that start very close can end up arbitrarily far apart, and the rate at which they diverge is exponential if they are chaotic. Such orbits --- which are solved for by deterministic equations of motion --- can have unpredictable outcomes.
Chaotic orbits are known to be important in the very centers of galaxies, near galactic bars, and in triaxial elliptical systems, but we are interested in the effect of chaos on the formation of tidal streams. This could have significant implications for dynamical inference and inference about the accretion history of galaxies based on observations of substructure.