Inflation and the scale dependent spectral index: Prospects and strategies

Peter Adshead, Richard Easther, Jonathan Pritchard, Abraham Loeb

Research output: Contribution to journalArticlepeer-review


We consider the running of the spectral index as a probe of both inflation itself, and of the overall evolution of the very early universe. Surveying a collection of simple single field inflationary models, we confirm that the magnitude of the running is relatively consistent, unlike the tensor amplitude, which varies by orders of magnitude. Given this target, we confirm that the running is potentially detectable by future large scale structure or 21 cm observations, but that only the most futuristic measurements can distinguish between these models on the basis of their running. For any specified inflationary scenario, the combination of the running index and unknown post-inflationary expansion history induces a theoretical uncertainty in the predicted value of the spectral index. This effect can easily dominate the statistical uncertainty with which Planck and its successors are expected to measure the spectral index. More positively, upcoming cosmological experiments thus provide an intriguing probe of physics between TeV and GUT scales by constraining the reheating history associated with any specified inflationary model, opening a window into the ''primordial dark age'' that follows the end of inflation.

Original languageEnglish (US)
Article number021
JournalJournal of Cosmology and Astroparticle Physics
Issue number2
StatePublished - Feb 2011
Externally publishedYes


  • cosmological parameters from CMBR
  • cosmological parameters from LSS
  • inflation

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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