Was there a negative vacuum energy in your past?
  A model for gravitational collapse where the event horizon is a quantum critical phase transition is extended to provide an explanation for the origin of the observable universe, where the expanding universe that we observe today was proceeded by a flat universe with a negative cosmological constant. In principal this allows one derive all the features of our universe from a single parameter: the magnitude of the pre-big bang negative vacuum energy density. In this paper a simple model for the big bang is introduced which allows us to relate the present day energy density and temperature fluctuations of the CMB, to the present day density of dark matter. This model for the big bang also makes a dramatic prediction: dark matter mostly consists of compact objects with a masses on the order of 10^4 solar masses. Remarkably this is consistent with numerical simulations for how primordial fluctuations in the density of dark give rise to the observed inhomogeneous distribution of matter in our universe. Our model for the big bang also allows for the production of some compact objects with masses greater than 10^4 solar masses, which is consistent with numerical simulations of structure formation which require massive primordial comapact objects as the seeds for galaxies in order to explain galactic morphologies. 
George Chapline and James Barbieri
gr-qc