Rotating cosmologies: classical and quantum
  We revisit spatially flat, anisotropic cosmologies within the framework of
mini-superspace. Putting special emphasis on the symmetries of the
mini-superspace action and on the associated conservation laws, we unveil a new
class of rotating cosmologies driven by solid matter. Their rotating is
physical, in that it is characterized in an invariant way in terms of a
conserved angular momentum. Along the way, we confirm the results of Bartolo et
al. regarding the slow decay of anisotropies for solid inflation. We then use
our minisuperspace approach as a laboratory to address certain puzzles of
quantum cosmology-among these, how to characterize the spacetime symmetries of
a quantum state at the level of the wavefunction of the universe. For the case
of a solid driven cosmology, this question seems better defined than in more
standard cases. Other questions remain unanswered, though; in particular, the
general question of how to operate a minisuperspace-like truncation of degrees
of freedom that is consistent at the quantum level.
