Probing the anisotropic expansion history of the universe with cosmic   microwave background
  We propose a simple technique to detect any anisotropic expansion stage in the history of the universe starting from the inflationary stage to the surface of last scattering from the CMBR data. We use the property that any anisotropic expansion in the universe would deform the shapes of the primordial density perturbations and this deformation can be detected in a shape analysis of superhorizon fluctuations in CMBR. Using this analysis we obtain the constraint on any previous anisotropic expansion of the universe to be less than about 35%. 
Ranjita K. Mohapatra, P. S. Saumia, Ajit M. Srivastava
astro-ph.CO gr-qc hep-ph