Anisotropic imprint of long-wavelength tensor perturbations on cosmic structure

Understand

Inflationary models predict a correlation between primordial density perturbations (scalar metric perturbations) and gravitational waves (tensor metric perturbations) in the form of a scalar-scalar-tensor three-point correlation, or bispectrum in Fourier space.

• The squeezed limit of this bispectrum implies a quadrupolar asymmetry in the observed local power spectrum for matter and galaxies.
• Here we show (like others before) that an infrared divergence in the amplitude of this power asymmetry predicted in single-field slow-roll models is canceled by projection effects when considering the observed power spectrum.
• We then further evaluate the nonzero, but finite, residual quadrupolar power asymmetry that remains after the divergences are canceled.