Conformal Transformations with Multiple Scalar Fields
  Many interesting models incorporate scalar fields with non-minimal couplings
to the spacetime Ricci curvature scalar. As is well known, if only one scalar
field is non-minimally coupled, then one may perform a conformal transformation
to a new frame in which both the gravitational portion of the Lagrangian and
the kinetic term for the (rescaled) scalar field assume canonical form. We
examine under what conditions the gravitational and kinetic terms in the
Lagrangian may be brought into canonical form when more than one scalar field
has non-minimal coupling. A particular class of two-field models admits such a
transformation, but models with more than two non-minimally coupled fields in
general do not.
