Seeking Inflation Fossils in the Cosmic Microwave Background

Abstract

If during inflation the inflaton couples to a "fossil" field, some new scalar, vector, or tensor field, it typically induces a scalar-scalar-fossil bispectrum. Even if the fossil field leaves no direct physical trace after inflation, it gives rise to correlations between different Fourier modes of the curvature or, equivalently, a nonzero curvature trispectrum, but without a curvature bispectrum. Here we quantify the effects of a fossil field on the cosmic microwave background (CMB) temperature fluctuations in terms of bipolar spherical harmonics (BiPoSHs). The effects of vector and tensor fossils can be distinguished geometrically from those of scalars through the parity of the BiPoSHs they induce. However, the two-dimensional nature of the CMB sky does not allow vectors to be distinguished geometrically from tensors. We estimate the detectability of a signal in terms of the scalar-scalar-fossil coupling for scalar, vector, and tensor fossils, assuming a local-type coupling. We comment on a divergence that arises in the quadrupolar BiPoSH from the scalar-scalar-tensor correlation in single-field slow-roll inflation.

10 pages, 5 figures

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• Imprints of Massive Primordial Fields on Large-Scale Structure
• The Pesky Power Asymmetry
• Inflationary tensor fossils in large-scale structure
• Distinctive signatures of space-time diffeomorphism breaking in EFT of inflation
• Anisotropic imprint of long-wavelength tensor perturbations on cosmic structure
• Non-Gaussianity from Axion-Gauge Fields Interactions during Inflation
• Missing Scalars at the Cosmological Collider
• Stable solutions of inflation driven by vector fields
• On the scalar consistency relation away from slow roll
• Fossilized Gravitational Wave Relic and Primordial Clocks
• Anisotropic tensor power spectrum at interferometer scales induced by tensor squeezed non-Gaussianity
• Photon-graviton scattering: A new way to detect anisotropic gravitational waves?
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• Possible Signatures of Inflationary Particle Content: Spin-2 Fields
• Numerical evaluation of the three-point scalar-tensor cross-correlations and the tensor bi-spectrum
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• The Physical Content of Long Tensor Modes in Cosmology
• Reconstructing the Long-wavelength Matter Density Fluctuation Modes from the Scalar-Type Clustering Fossils
• Inflationary tensor fossils deformed by solid matter -- scalar field interaction
• Non-Gaussianity of Tensor Induced Density Perturbations
• The scalar-scalar-tensor inflationary three-point function in the axion monodromy model