Constraining Modified Gravity with Large non-Gaussianities
| dc.creator | Vazquez, Samuel E. | |
| dc.date | 2008-06-03 | |
| dc.date | 2008-06-17 | |
| dc.date.accessioned | 2026-07-07T12:51:10Z | |
| dc.date.available | 2026-07-07T12:51:10Z | |
| dc.description | In writing a covariant effective action for single field inflation, one is allowed to add a Gauss-Bonnet and axion-type curvature couplings. These couplings represent modifications of gravity, and are the unique higher-curvature terms that lead to second order equations of motion in four dimensions. In this paper we study the observational consequences of such couplings for models with large non-gaussianities. Our focus is on the Gauss-Bonnet term. In particular, we study an effective action where the scalar Lagrangian is a general function of the inflaton and its first derivative. We show that, for large non-gaussianities, one can write $f_{NL}$ in terms of only three parameters. The shape of $f_{NL}$ is also studied, and we find that it is very similar to that of k-inflation. We show that the Gauss-Bonnet term enhances the production of gravitational waves, and allows a smaller speed of sound for scalar perturbations. This, in turn, can lead to larger non-gaussianities which can be constrained by observations. Using current WMAP limits on $f_{NL}$ and the tensor/scalar ratio, we put constraints on all parameters. As an example, we show that for DBI inflation, the Gauss-Bonnet coupling leads to an interesting observational window with both large $f_{NL}$ and a large amplitude of gravitational waves. Finally, we show that the Gauss-Bonnet coupling admits a de-Sitter phase with a relativistic dispersion relation for scalar perturbations. | |
| dc.description | 17 pages, 7 figures, RevTeX format | |
| dc.identifier | https://arxiv.org/abs/0806.0603 | |
| dc.identifier | http://arxiv.org/abs/0806.0603 | |
| dc.identifier | Phys.Rev.D79:043520,2009 | |
| dc.identifier | doi:10.1103/PhysRevD.79.043520 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/222905 | |
| dc.subject | High Energy Physics - Theory | |
| dc.subject | Astrophysics | |
| dc.subject | General Relativity and Quantum Cosmology | |
| dc.title | Constraining Modified Gravity with Large non-Gaussianities | |
| dc.type | text |