We investigate how the background evolution affects the curvature perturbations generated by the curvaton, assuming a curvaton potential that may deviate slightly from the quadratic one, and parameterizing the background fluid density as ρ\propto a^{-α}, where a is the scale factor, and αdepends on the background fluid. It turns out that the more there is deviation from the quadratic case, the more pronounced is the dependence of the curvature perturbation on α. We also show that the background can have a significant effect on the nonlinearity parameters f_NL and g_NL. As an example, if at the onset of the curvaton oscillation there is a dimension 6 contribution to the potential at 5 % level and the energy fraction of the curvaton to the total one at the time of its decay is at 1 %, we find variations Δf_NL \sim \mathcal{O}(10) and Δg_NL \sim \mathcal{O}(10^4) between matter and radiation dominated backgrounds. Moreover, we demonstrate that there is a relation between f_NL and g_NL that can be used to probe the form of the curvaton potential and the equation of state of the background fluid.
We revise the Non-Gaussianity of canonical curvaton scenario with a generalized $δN$ formalism, in which it could handle the generic potentials. In various curvaton models, the energy density is dominant in different period including the secondary inflation of curvaton, matter domination and radiation domination. Our method could unify to deal with these periods since the non-linearity parameter $f_{\rm NL}$ associated with Non-Gaussianity is a function of equation of state $w$. We firstly investigate the most simple curvaton scenario, namely the chaotic curvaton with quadratic potential. Our …
In general relativity predictions for observable quantities can be expressed in a coordinate independent way. Nonetheless it may be inconvenient to do so. Using a particular frame may be the easiest way to connect theoretical predictions to measurable quantities. For the cosmological curvature bispectrum such frame is described by the Conformal Fermi Coordinates. In single field inflation it was shown that going to this frame cancels the squeezed limit of the density perturbation bispectrum calculated in Global Coordinates. We explore this issue in quasi single field inflation when the curvato…
Memoirs of the curvaton: non-perturbative non-Gaussianity and supermassive primordial black holes
Keemilise ja Bioloogilise Füüsika Instituut（化学与生物物理研究所）；Tallinn University of Technology（塔林科技大学）；Center for Astrophysics and Space Science (CASS), New York University Abu Dhabi（纽约大学阿布扎比分校天体物理学与空间科学中心）
研究曲率子超出二次势的自相互作用，通过简化作用量构建非高斯映射，发现自相互作用可增强或抑制非高斯性，并利用强正非高斯性在COBE/FIRAS约束下产生超大质量原初黑洞种子，解释JWST观测的Little Red Dots。
We develop a complete set of tools for CMB forecasting, simulation and estimation of primordial running bispectra, arising from a variety of curvaton and single-field (DBI) models of Inflation. We validate our pipeline using mock CMB running non-Gaussianity realizations and test it on real data by obtaining experimental constraints on the $f_{\rm NL}$ running spectral index, $n_{\rm NG}$, using WMAP 9-year data. Our final bounds (68\% C.L.) read $-0.6< n_{\rm NG}<1.4$, $-0.3< n_{\rm NG}<1.2$, $-1.1<n_{\rm NG}<0.7$ for the single-field curvaton, two-field curvaton and DBI scenarios, respectivel…
Primordial non-Gaussianity signatures of extremely heavy particles are re-examined within a simple alternative to the standard inflationary paradigm, in which the primordial fluctuations and the inflationary spacetime expansion are sourced by two different fields. The curvaton scenario provides an example of this in which the distinct roles are played by the curvaton and the inflaton fields, respectively. We study couplings of the curvaton to heavy particles with masses of order the inflationary Hubble scale, and show that they can lead to non-Gaussian signals orders of magnitude larger than t…
We revise primordial black hole (PBH) formation in the axion-like curvaton model and investigate whether PBHs formed in this model can be the origin of the gravtitational wave (GW) signals detected by the Advanced LIGO. In this model, small-scale curvature perturbations with large amplitude are generated, which is essential for PBH formation. On the other hand, large curvature perturbations also become a source of primordial GWs by their second-order effects. Severe constraints are imposed on such GWs by pulsar timing array (PTA) experiments. We also check the consistency of the model with the…
