Rescaled extrapolation for vector-valued functions
  We extend Rubio de Francia's extrapolation theorem for functions valued in
UMD Banach function spaces, leading to short proofs of some new and known
results. In particular we prove Littlewood-Paley-Rubio de Francia-type
estimates and boundedness of variational Carleson operators for Banach function
spaces with UMD concavifications.
