Cosmological observables, IR growth of fluctuations, and scale-dependent anisotropies

Steven B. Giddings, Martin Snoager Sloth

Research output: Contribution to journalJournal articleResearchpeer-review


We extend semiclassical methods in inflationary cosmology that capture leading IR corrections to correlators. Such large IR effects can be absorbed into a coordinate change when examining sufficiently local observables, but not when comparing observations at large separation in scales, such as seen by a late-time observer. The analysis is facilitated by definition of a scale-dependent metric and physical momentum. These assist definition of "IR-safe" observables seen by a post-inflationary observer, which are contrasted to those based on the local geometry of the reheating surface. For such observables, the observer's horizon provides an effective IR cutoff. IR growth contributes to enhanced statistical inhomogeneities/anisotropies at short scales, observation of which by a present day observer might be sought in 21 cm measurements. Such IR corrections are argued to grow large for a very late-time observer.
Original languageEnglish
Article number063528
Issue number6
Number of pages7
Publication statusPublished - 2011
Externally publishedYes


  • hep-th
  • astro-ph.CO
  • gr-qc

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