Generating the curvature perturbation without an inflaton

By D. Lyth, D. Wands. 2001

1,238 citations recorded by the source corpus.

We present a mechanism for the origin of the large-scale curvature perturbation in our Universe by the late decay of a massive scalar field, the curvaton. The curvaton is light during a period of cosmological inflation, when it acquires a perturbation with an almost scale-invariant spectrum. This corresponds initially to an isocurvature density perturbation, which generates the curvature perturbation after inflation when the curvaton density becomes a significant fraction of the total. The isocurvature density perturbation disappears if the curvaton completely decays into thermalised radiation. Any residual isocurvature perturbation is 100% correlated with the curvature. The same mechanism can also generate the curvature perturbation in pre-big bang/ekpyrotic models, provided that the curvaton has a suitable non-canonical kinetic term so as to generate a flat spectrum.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a466fd4dfcf8d3e2ce71d29a7deb74b4eaac5acc

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Citations in the corpus

An infinite set of Ward identities for adiabatic modes in cosmology (2013, background): “Conversely, to observe a significant 3-point function in this limit requires violating one of the assumptions above, for instance through additional scalar fields [23–28] or an unstable background [29, 30, 33, 34].”
Primordial black holes from inflation and non-Gaussianity (2018, background): “The idea is that there is a curvaton-like field σ [69] with quadratic potential”
Galilean Genesis: An Alternative to inflation (2010, background): “The conversion of σ fluctuations into adiabatic ones can happen through one of the mechanisms that have been studied at length for inflation: σ may change the way π reheats the Universe [11, 12], or become relevant at a later epoch [13].”
Primordial non-Gaussianities from multiple-field inflation (2005, background): “This actually occurs, for example, in the curvaton scenario [42]–[44], [14, 15].”
Probing String Theory with Modulated Cosmological Fluctuations (2003, background): “This mechanism has some common features with the curvaton scenario [15].”
A smooth bouncing cosmology with scale invariant spectrum (2007, background): “A further possibility is that δψ fluctuations are converted only in the expanding phase, as in the curvaton [30] and variable decay models [31].”
Testing for Non-Gaussianity in the Wilkinson Microwave Anisotropy Probe Data: Minkowski Functionals and the Length of the Skeleton (2004, background): “Second, most current theories predict a Gaussian (or at least nearly Gaussian) anisotropy field, and significant departures from Gaussianity could point toward new physics (e.g., Wang & Kamionkowski 2000; Lyth & Wands 2002; Bouchet et al. 2002; Bernardeau & Uzan 2003).”
Planck2018 results (2018, background): “Once fully (or almost fully) dominating the energy density of the Universe, this curvaton field decays either to CDM or to other species (Mollerach 1990; Linde & Mukhanov 1997; Enqvist & Sloth 2002; Moroi & Takahashi 2001; Lyth & Wands 2002; Bartolo & Liddle 2002; Lyth et al. 2003).”