We investigate the possibility that dark energy does not couple to
gravitation in the same way than ordinary matter, yielding a violation of the
weak and strong equivalence principles on cosmological scales. We build a
transient mechanism in which gravitation is pushed away from general relativity
by a Born-Infeld gauge interaction acting as an "Abnormally Weighting" (dark)
Energy. This mechanism accounts for the Hubble diagram of far-away supernovae
by cosmic acceleration and time variation of the gravitational constant while
accounting naturally for the present tests on general relativity.Comment: 5 pages, 3 figures, sequel of Phys. Rev. D 73 023520 (2006), to
appear in Physical Review Letter