Nonsingularity of Flat Robertson-Walker Models in the Special   Relativistic Approach to Einstein's Equations
  Recently the neglected issue of the causal structure in the flat spacetime approach to Einstein's theory of gravity has been substantially resolved. Consistency requires that the flat metric's null cone be respected by the null cone of the effective curved metric. While consistency is not automatic, thoughtful use of the naive gauge freedom resolves the problem. After briefly recapitulating how consistent causality is achieved, we consider the flat Robertson-Walker Big Bang model. The Big Bang singularity in the spatially flat Robertson-Walker cosmological model is banished to past infinity in Minkowski spacetime. A modified notion of singularity is proposed to fit the special relativistic approach, so that the Big Bang becomes nonsingular. 
J. Brian Pitts, W. C. Schieve