Observational signatures and non-Gaussianities of general single-field inflation

By Xingang Chen, Min-xin Huang, S. Kachru, Gary Shiu. 2006

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We perform a general study of primordial scalar non-Gaussianities in single-field inflationary models in Einstein gravity. We consider models where the inflaton Lagrangian is an arbitrary function of the scalar field and its first derivative, and the sound speed is arbitrary. We find that under reasonable assumptions, the non-Gaussianity is completely determined by five parameters. In special limits of the parameter space, one finds distinctive ‘shapes’ of the non-Gaussianity. In models with a small sound speed, several of these shapes would become potentially observable in the near future. Different limits of our formulae recover various previously known results.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Oceanography

View Paper: https://www.semanticscholar.org/paper/8a4079bf72be8c9bf81c478a8f69ba6f3928a652

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Citations in the corpus

Inflationary trispectrum from graviton exchange (2008, result): “In this limit, the trispectrum must be described by Maldacena’s consistency relation [11, 46, 26, 47, 45]: the scalar mode associated with the small momentum forms a fixed classical background into which the remaining modes exit, in a similar fashion to the calculations discussed in §3.”
An infinite set of Ward identities for adiabatic modes in cosmology (2013, background): “The 3-point amplitude from ζ̇3 takes the simple form [71]”
SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2010, background): “There are various other models that can produce f equilNL (Arkani-Hamed et al. 2004; Seery & Lidsey 2005; Chen et al. 2007; Cheung et al. 2008; Li et al. 2008).”
Phenomenology of a pseudo-scalar inflaton: naturally large nongaussianity (2011, methodology): “To obtain observable nongaussianity, previous studies have invoked non-standard field theories (involving small sounds speed [23] or higher derivatives [5]), or initial conditions [23, 24, 25, 26], potentials with sharp features [27, 28], dissipative effects [3], fine-tuned inflationary trajectories”
Large-scale bias and efficient generation of initial conditions for nonlocal primordial non-Gaussianity (2011, background): “Relaxing the assumption of initial vacuum states leads to the so-called folded shape [14, 19], which gives”
Gauge Field Production in Axion Inflation: Consequences for Monodromy, non-Gaussianity in the CMB, and Gravitational Waves at Interferometers (2011, background): “1 For example: small sound speed [5], higher derivatives [6], special initial conditions [7, 8, 11], potentials with sharp features [12, 13], dissipative effects [14, 15], turning trajectories [16], post-inflationary effects (such as preheating [17, 18]), etc.”
The DESI Experiment Part I: Science,Targeting, and Survey Design (2016, background): “Recently, a number of inflationary models have been proposed which predict a potentially observable level of non-Gaussianity, these include those from fast-roll inflation [130, 131, 132, 133, 134], quasi-single field inflation [135, 136], warm inflation [137, 138], and non-Bunch-Davies or excited in”
On soft limits of inflationary correlation functions (2012, background): “The effects of excited initial states on primordial non-Gaussianity have been explored in [35–40].”
Gauge fields and inflation (2012, methodology): “Besides that, the possible parameter space for the models which can provide significant non-Gaussianity, such as K-inflation models with small sound speeds c(2)s ≪ 1 [34] are mainly shrunk by the constraints on the non-Gaussianity parameters.”
Inflation and String Theory (2014, background): “correspondingly small [121,122,264]: ∣∣f equil NL ∣∣ ∼ 1 c(2)s − 1 ≈ X Λ(4) + · · · 1 .”
Primordial Non-Gaussianities from Inflation Models (2010, methodology): “For bispectra that are approximately scale invariant, the shape is a more important property [50, 60].”
On the consistency relation of the three-point function in single-field inflation (2007, methodology): “Such corrections have been treated before [4, 23], but we will not need them in our calculation.”
Inflation, Cosmic Perturbations and Non-Gaussianities (2013, background): “For non-Gaussianities, the leading order terms in the slow roll approximation is [145]”
A Mellin space approach to cosmological correlators (2019, background): “The correlators should be non-singular in such configurations, which is related to the adiabatic vacuum condition [102–106].”