http://arxiv.org/abs/2010.03973
We study the slow-roll single field inflation in the context of the consistent $D\to4$ Einstein-Gauss-Bonnet gravity that was recently proposed in \cite{Aoki:2020lig}. In addition to the standard attractor regime, we find a new attractor regime which we call the Gauss-Bonnet attractor as the dominant contribution comes from the Gauss-Bonnet term. Around this attractor solution, we find power spectra and spectral tilts for the curvature perturbations and gravitational waves (GWs) and also a model-independent consistency relation among observable quantities. The Gauss-Bonnet term provides a nonlinear $k^4$ term to the GWs dispersion relation which has the same order as the standard linear $k^2$ term at the time of horizon crossing around the Gauss-Bonnet attractor. The Gauss-Bonnet attractor regime thus provides a new scenario for the primordial GWs which can be tested by observations. Finally, we study non-Gaussianity of GWs in this model and estimate the nonlinear parameters $f^{s_1s_2s_3}{\rm NL,\;sq}$ and $f^{s_1s_2s_3}{\rm NL,\;eq}$ by fitting the computed GWs bispectra with the local-type and equilateral-type templates respectively at the squeezed limit and at the equilateral shape. For helicities $(+++)$ and $(—)$, $f^{s_1s_2s_3}{\rm NL,\;sq}$ is larger while $f^{s_1s_2s_3}{\rm NL,\;eq}$ is larger for helicities $(++-)$ and $(–+)$.
K. Aoki, M. Gorji, S. Mizuno, et. al.
Fri, 9 Oct 20
6/64
Comments: 29 pages, 4 figures