Emergent Cosmology Revisited
  We explore the possibility of emergent cosmology using the effective
potential formalism. We discover new models of emergent cosmology which satisfy
the constraints posed by the cosmic microwave background (CMB). We demonstrate
that, within the framework of modified gravity, the emergent scenario can arise
in a universe which is spatially open/closed. By contrast, in general
relativity (GR) emergent cosmology arises from a spatially closed past-eternal
Einstein Static Universe (ESU). In GR the ESU is unstable, which creates fine
tuning problems for emergent cosmology. However, modified gravity models
including Braneworld models, Loop Quantum Cosmology (LQC) and Asymptotically
Free Gravity result in a stable ESU. Consequently, in these models emergent
cosmology arises from a larger class of initial conditions including those in
which the universe eternally oscillates about the ESU fixed point. We
demonstrate that such an oscillating universe is necessarily accompanied by
graviton production. For a large region in parameter space graviton production
is enhanced through a parametric resonance, casting serious doubts as to
whether this emergent scenario can be past-eternal.
