From big crunch to big bang

Abstract

We consider conditions under which a universe contracting towards a big crunch can make a transition to an expanding big bang universe. A promising example is 11-dimensional M-theory in which the eleventh dimension collapses, bounces, and re-expands. At the bounce, the model can reduce to a weakly coupled heterotic string theory and, we conjecture, it may be possible to follow the transition from contraction to expansion. The possibility opens the door to new classes of cosmological models. For example, we discuss how it suggests a major simplification and modification of the recently proposed ekpyrotic scenario.

The failure of cosmological perturbation theory in the new ekpyrotic and cyclic ekpyrotic scenarios

“…This problem is clearly recognized in [21] ("there is concern that the quantum fluctuations become uncontrolled at t = 0"). Nevertheless, the action of Eq.…”

“…The general idea of the new ekpyrotic scenario, developed in an earlier related paper [21], is that the underlying five-dimensional theory is non-singular as one goes through the bounce, so that it may in some sense be permissible to allow the four-dimensional scale factor to go through zero. The standard field theory action Eq.…”

Probing the cosmological singularity with a particle

“…, N − 2). One term in the metric (4) disappears/appears at t = 0, thus the CM space may be used to model the big-crunch/big-bang type singularity [8]. In what follows we restrict our considerations to the 2d CM space.…”

“…It is based on the idea of a cyclic evolution, CE, of the Universe. The ST model has been inspired by string/M theories [8]. In its simplest version it assumes that the spacetime can be modelled by the higher dimensional compactified Milne, CM, space.…”

Aspects of String Cosmology

“…See e.g. [23][24][25][26][27][28] [10] for work towards this end. This endeavor is both technically and conceptually challenging.…”