The Multidimensional Milky Way
  Studying our Galaxy, the Milky Way (MW), gives us a close-up view of the
interplay between cosmology, dark matter, and galaxy formation. In the next
decade our understanding of the MW's dynamics, stellar populations, and
structure will undergo a revolution thanks to planned and proposed astrometric,
spectroscopic and photometric surveys, building on recent advances by the Gaia
astrometric survey. Together, these new efforts will measure three-dimensional
positions and velocities and numerous chemical abundances for stars to the MW's
edge and well into the Local Group, leading to a complete multidimensional view
of our Galaxy. Studies of the multidimensional Milky Way beyond the Gaia
frontier---from the edge of the Galactic disk to the edge of our Galaxy's dark
matter halo---will unlock new scientific advances across astrophysics, from
constraints on dark matter to insights into galaxy formation.
