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Related Experiment Videos

Inflation versus cyclic predictions for spectral tilt.

Justin Khoury1, Paul J Steinhardt, Neil Turok

  • 1ISCAP, Columbia University, New York, New York 10027, USA.

Physical Review Letters
|November 13, 2003
PubMed
Summary

This study compares inflationary and cyclic universe models, finding they predict identical primordial density spectral tilts (n(s) ≈ 0.95). Inflation also predicts a significant tensor-to-scalar ratio (T/S ≈ 20%).

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Area of Science:

  • Cosmology
  • Theoretical Physics
  • Astrophysics

Background:

  • Cosmic inflation and ekpyrotic/cyclic models are leading theories for the early universe.
  • Understanding primordial density inhomogeneities is key to testing these models.

Purpose of the Study:

  • To provide a nearly model-independent estimate comparing inflationary and ekpyrotic/cyclic models.
  • To predict the spectral tilt of primordial density inhomogeneities for these models.

Main Methods:

  • Developed a model-independent estimation technique.
  • Calculated predictions for the spectral tilt (n(s)).
  • Estimated the tensor-to-scalar ratio (T/S) for inflationary models.

Main Results:

  • Both inflationary and ekpyrotic/cyclic models yield an identical spectral tilt, n(s) ≈ 0.95.
  • Inflationary models predict a tensor-to-scalar ratio of T/S ≈ 20% for low multipoles of cosmic microwave background anisotropy.
  • The tensor contribution is negligible for ekpyrotic/cyclic models.

Conclusions:

  • The spectral tilt prediction n(s) ≈ 0.95 offers a testable constraint for simple inflationary and ekpyrotic/cyclic models.
  • The tensor-to-scalar ratio provides a key differentiator between inflationary and ekpyrotic/cyclic scenarios.

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