When scalar field is kinetically coupled to the Einstein tensor
  We explore the cosmic evolution of a scalar field with the kinetic term
coupled to the Einstein tensor. We find that, in the absence of other matter
sources or in the presence of only pressureless matter, the scalar behaves as
pressureless matter and the sound speed of the scalar is vanishing. These
properties enable the scalar field to be a candidate of cold dark matter. By
also considering the scalar potential, we find the scalar field may play the
role of both dark matter and dark energy. In this case, the equation of state
of the scalar can cross the phantom divide, but this can lead to the sound
speed becoming superluminal as it crosses the divide, and so is physically
forbidden. Finally, if the kinetic term is coupled to more than one Einstein
tensor, we find the equation of state is always approximately equal to -1
whether the potential is flat or not, and so the scalar may also be a candidate
for the inflaton.
