Accretion and Diffusion Timescales in Sheets and Filaments
  A comparison of accretion and (turbulent) magnetic diffusion timescales for
sheets and filaments demonstrates that dense star-forming clouds generally will
-- under realistic conditions -- become supercritical due to mass accretion on
timescales at least an order of magnitude shorter than ambipolar and/or
turbulent diffusion timescales. Thus, ambipolar or turbulent diffusion -- while
present -- is unlikely to control the formation of cores and stars.
