Reconstructing the EFT of inflation from cosmological data

Abstract

Reconstructions of the primordial power spectrum (PPS) of curvature perturbations from cosmic microwave background anisotropies and large-scale structure data suggest that the usually assumed power-law PPS has localised features (up to ∼ 10% in amplitude), although of only marginal significance in the framework of ΛCDM cosmology. On the other hand if the cosmology is taken to be Einstein-de Sitter, larger features in the PPS (up to ∼ 20% in amplitude) are required to accurately fit the observed acoustic peaks. Within the context of single clock inflation, we show that any given reconstruction of the PPS can be mapped on to functional parameters of the underlying effective theory of the adiabatic mode within a 2ndorder formalism, provided the best fit fractional change of the PPS, ∆P R /P R is such that (∆P R /P R ) 3 falls within the 1 σ confidence interval of the reconstruction for features induced by variations of either the sound speed c s or the slow-roll parameter . Although there is a degeneracy amongst these functional parameters (and the models that project onto them), we can identify simple representative inflationary models that yield such features in the PPS. Thus we provide a dictionary (more accurately, a thesaurus) to go from observational data, via the reconstructed PPS, to models that reproduce them to per cent level precision.

Bayesian reconstruction of the inflaton's speed of sound using CMB data

“…If the noise is reduced, we could discern how realistic the reductions at earlier conformal times are. Moreover, we also consider introducing new features coming from a variable first slow-roll parameter [18] to perform a joint search of both patterns: features induced by a variable c s (τ ) and (τ ). These profiles of u(τ ) show only one single reduction of the inflaton's speed of sound or one dip.…”

“…Reconstructions at the level of the primordial power spectrum have already been attempted [12][13][14][15][16][17][18][19]. However, there is not enough constraining power in Planck's power spectrum alone to decide on a particular model for the features.…”

Curvature perturbations from stochastic particle production during inflation

“…However, most high-energy completions of the Standard Model include many interacting fields at inflationary energies [9], whose dynamics need not a priori be simple. It is still plausible that the field content during inflation is rich, and their dynamics are complex, leading to features in the power spectrum and higher-point correlators (see, for example, [6,8,10]) which might have been missed in the data so far. Important consequences might also arise from features in the power spectrum that lie beyond the scales relevant for the cosmic microwave background (CMB) and large-scale structure (LSS), but could be relevant to, for example, primordial black hole formation [11,12], reheating [13,14], and CMB spectral distortions [7,15].…”

Curvature Perturbations From Stochastic Particle Production During Inflation

“…(2.5)) includes a term independent of ζ, and a linear response (dissipation) term that has correlations with curvature perturbations. 10 Because of such correlations, it is a-priori not possible to ignore the contribution of the linear response when calculating the sourced curvature power spectrum based just on the smallness of ζ. However, it is still plausible to ignore the linear response contribution to ∆ 2 ζ .…”

“…However, most high-energy completions of the Standard Model include many interacting fields at inflationary energies [9], whose dynamics need not a priori be simple. It is still plausible that the field content during inflation is rich, and their dynamics are complex, leading to features in the power spectrum and higher-point correlators (see, for example, [6,8,10]) which might have been missed in the data so far. Important consequences might also arise from features in the power spectrum that lie beyond the scales relevant for the cosmic microwave background (CMB) and large-scale structure (LSS), but could be relevant to, for example, primordial black hole formation [11,12], reheating [13,14], and CMB spectral distortions [7,15].…”