Ekpyrotic universe
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The ekpyrotic universe, or ekpyrotic scenario, is a cosmological model of the origin and shape of the universe. The name comes from a Stoic term ekpyrosis (Ancient Greek Template:Lang ekpurōsis) meaning conflagration or in Stoic usage "conversion into fire". The ekpyrotic model of the universe is an alternative to the standard cosmic inflation model for the very early universe; both models accommodate the standard Big Bang Lambda-CDM model of our universe. The ekpyrotic model is a precursor to, and part of, some cyclic models.
The ekpyrotic model came out of work by Neil Turok and Paul Steinhardt and maintains that the universe did not start in a singularity, but came about from the collision of two branes. This collision avoids the primordial singularity while preserving nearly scale-free density fluctuations and other features of the observed universe. The ekpyrotic model is cyclic, though collisions between branes are rare on the time scale of the expansion of the universe to a nearly featureless flat expanse. Observations that may distinguish between the ekpyrotic and inflationary models include polarization of the cosmic microwave background radiation and frequency distribution of the gravitational wave spectrum.
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