Searching for Fossil Fields in the Gravity Sector

Abstract: 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 can modulate the power spectrum inducing a sizable quadrupolar anisotropy. We investigate how this dynamics plays out for the tensor two-point correlator. The resulting quadrupole stores information on squeezed tensor non-Gaussianities, specifically those sourced by the 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 CMB scales through the detection of B-modes, they are accessible at smaller scales via interferometers and pulsar timing arrays.