Searching for fossil fields in the gravity sector

Emanuela Dimastrogiovanni*, Matteo Fasiello, Gianmassimo Tasinato

*Corresponding author for this work

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Evidence for the presence of extra fields during inflation may be found in the anisotropies of the scalar and tensor spectra across a vast range of scales. Indeed, beyond the single-field slow-roll paradigm, a long tensor mode modulating the power spectrum can induce a sizable quadrupolar anisotropy. We investigate how these dynamics play out for the tensor two-point correlator. The resulting quadrupole stores information on squeezed tensor non-Gaussianities, including those sourced by extra field content and responsible for the breaking of so-called consistency relations. We underscore the potential of anisotropies as a probe of new physics: testable at cosmic microwave background scales through the detection of B modes, they are accessible at smaller scales via pulsar timing arrays and interferometers. Our findings are particularly relevant in that recent studies show a considerable suppression for tensor non-Gaussianities if all modes are well inside the horizon. Quadrupolar anisotropies instead probe an unsuppressed ultrasqueezed bispectrum where the long mode can be horizon size.

Original languageEnglish
Article number061302
Number of pages6
JournalPhysical Review Letters
Issue number6
Early online date12 Feb 2020
Publication statusPublished - 14 Feb 2020


  • RCUK
  • STFC
  • ST/S000550/1
  • ST/P00055X/1


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