  We argue that Einstein gravity coupled to a Born-Infeld theory provides an
attractive candidate to represent dark matter and dark energy. For cosmological
models, the Born-Infeld field has an equation of state which interpolates
between matter, w=0 (small times), and a cosmological constant w=-1 (large
times). On galactic scales, the Born-Infeld field predicts asymptotically flat
rotation curves.
