A Matter Bounce By Means of Ghost Condensation
Assuming the existence of a scalar field which undergoes "ghost condensation" and which has a suitably chosen potential, it is possible to obtain a non-singular bouncing cosmology in the presence of regular matter and radiation. The potential for the ghost condensate field can be chosen such that the cosmological bounce is stable against the presence of anisotropic stress. Cosmological fluctuations on long wavelengths relevant to current cosmological observations pass through the bounce unaffected by the new physics which yields the bounce. Thus, this model allows for the realization of the "matter bounce" scenario, an alternative to inflationary cosmology for the generation of the observed primordial fluctuations in which the inhomogeneities originate as quantum vacuum perturbations which exit the Hubble radius in the matter-dominated phase of contraction.