Inflation versus cyclic predictions for spectral tilt

Justin Khoury, Paul J. Steinhardt, Neil Turok

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


We present a nearly model-independent estimate that yields the predictions of a class of simple inflationary and ekpyrotic or cyclic models for the spectral tilt of the primordial density inhomogeneities that enables us to compare the two scenarios. Remarkably, we find that the two produce an identical result, [Formula presented]. For inflation, the same estimate predicts a ratio of tensor to scalar contributions to the low [Formula presented] multipoles of the microwave background anisotropy of [Formula presented]; the tensor contribution is negligible for ekpyrotic or cyclic models, as shown in earlier papers.

Original languageEnglish (US)
JournalPhysical review letters
Issue number16
StatePublished - 2003

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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