Editorial: Highlight notes on Semiclassical suppression of weak anisotropies of a generic universe


Observational evidence strongly suggests that we are currently living in a Universe that can be described by an expanding Friedmann-Robertson-Walker cosmology, i.e. a Universe that to a high degree is homogeneous and isotropic. It contains a negligible fraction of known ordinary (baryonic) matter, a substantial fraction of dark matter being, however, insufficient of closing and retarding the Universe, and some unknown kind of dark energy which causes the Universe to expand in an accelerated manner. This Universe should have begun in an inflationary initial phase which is believed to have been subject to quantum effects involving the yet to be identified quantum gravity and thus must be described by kind of a quantum cosmology. Application of quantum theory to the entire Universe poses some problems as the definition of a single wave function for the whole lacks an unambiguous meaning and interpretation. No measurements can be made on the wave function from inside the Universe. Initially the Universe was highly inhomogeneous and anisotropic, and correspondingly the wave function was highly inhomogeneous and anisotropic as well. How then did it proceed to become the wave function of the current homogeneous and isotropic Universe as it is observed today? For an initially anisotropic Universe the present paper solves this problem in a clever way. It considers the dynamics of a generic cosmological model in which the anisotropies are restricted to be quantum effects on an expanding homogeneous cosmology which is described by the (time- and space-dependent) semi-classical scale factor a(t, xi). The changes of its shape due to anisotropy, are included in quantum coordinates. The problem is treated in a perturbation theoretical way, with the anisotropies acting as quantum perturbations and assuming that the radius and shape of the Universe are of different physical nature. This assumption allows factorizing the wave function into semi-classical and quantum factors. Carrying through this program in the Wheeler-De Witt equation for the evolution of the wave function, the radial expansion of the Universe asymptotically damps away the initial anisotropies when the Universe becomes sufficiently large. Its properties far from the initial singularity gradually approach those of an isotropic (and by assumption homogeneous) Friedmann-Robertson-Walker cosmology thereby reproducing an important property of the present state of the Universe as the most probable universal state that can be realized during the quantum evolution of the Universe.

  author = {Treumann, R.A.},
  doi = {10.1209/0295-5075/86/60000},
  journal = {Europhys. Lett.},
  language = {en},
  number = {6},
  pages = {60000},
  title = {Editorial: Highlight notes on Semiclassical suppression of weak anisotropies of a generic universe},
  volume = {86},
  year = {2009},
%O Journal Article
%A Treumann, R.A.
%R 10.1209/0295-5075/86/60000
%J Europhys. Lett.
%G en
%N 6
%P 60000
%T Editorial: Highlight notes on Semiclassical suppression of weak anisotropies of a generic universe
%V 86
%D 2009