How to Avoid a Swift Kick in the Chameleons
  Recently it was argued that the conformal coupling of the chameleon to matter
fields created an issue for early universe cosmology. As standard model degrees
of freedom become non-relativistic in the early universe the chameleon is
attracted towards a "surfing" solution, so that it arrives at the potential
minimum with too large a velocity. This leads to rapid variations in the
chameleon's mass and excitation of high energy modes, casting doubts on the
classical treatment at Big Bang Nucleosynthesis. Here we present the DBI
chameleon, a consistent high energy modification of the chameleon theory that
dynamically renders it weakly coupled to matter during the early universe
thereby eliminating the adverse effects of the `kicks'. This is done without
any fine tuning of the coupling between the chameleon and matter fields and
retains its screening ability in the solar system. We demonstrate this
explicitly with a combination of analytic and numerical results.
