Features and new physical scales in primordial observables: Theory and observation

By J. Chluba, Jan Hamann, S. Patil. 2015

230 citations recorded by the source corpus.

All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, ϵ), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well-grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background (CMB) anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure (LSS) and potentially, 21 cm surveys.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fbae6ca15b90f85e480ec2b1f5377f2df6678206

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Citations in the corpus

Non-Gaussianity and the induced gravitational wave background (2021, background): “= 0.05h Mpc−1 required by the CMB anisotropies, is unobservably tiny [32, 33].”
Primordial black holes and second order gravitational waves from ultra-slow-roll inflation (2017, background): “In fact, almost all the number of e-folds comes from the contribution around φinfl, then the power spectrum gets big boost in the small scales, this will cause big μ distortion [50, 64] because the μ distortion is [64, 65] μac ≈ ∫ ∞”
Steepest growth of the power spectrum and primordial black holes (2018, background): “Any heat dissipated into the primordial plasma has the possibility of showing up in the form of μ and y type distortions of the CMB ([90, 91]), provided they occur in the redshift window between z ∼ 106 and last scattering at z ∼ 103.”
Planck2018 results (2018, background): “…power spectrum reconstruction methods of the previous section are an excellent way to search for coarse features in the spectrum, but lack the resolution to detect the higher-frequency features generically predicted by various physical mechanisms [see, e.g., Chluba et al. (2015) for a review].”
Exploring cosmic origins with CORE: Inflation (2016, background): “A variety of physical processes can generate spectral features at any time during or after inflation (see [141] for a review).”