The Conformal Stealth of any Standard Cosmology
  It is shown that any homogeneous and isotropic universe, independently of its
spatial topology and matter content, allows for the presence of a conformal
stealth, i.e. a nontrivial conformally invariant scalar field with vanishing
energy-momentum tensor, which evolves along with the universe without causing
even the smallest backreaction. Surprisingly, this gravitationally invisible
universal witness is inhomogeneous with zero consequences for the underlying
cosmology. Additionally, it is shown that these results are not exclusive of a
four-dimensional universe by generalizing them to higher dimensions.
