Non-Gaussianities in multi-field inflation

By T. Battefeld, R. Easther. 2006

205 citations recorded by the source corpus.

We compute the amplitude of the non-Gaussianities in inflationary models with multiple, uncoupled scalar fields. This calculation thus applies to all models of assisted inflation, including N-flation, where inflation is driven by multiple axion fields arising from shift symmetries in a flux stabilized string vacuum. The non-Gaussianities are associated with nonlinear evolution of the field (and density) perturbations, characterized by the parameter fNL. We derive a general expression for the nonlinear parameter, incorporating the evolution of perturbations after horizon-crossing. This is valid for arbitrary separable potentials during slow roll. To develop an intuitive understanding of this system and to demonstrate the applicability of the formalism we examine several cases with quadratic potentials: two-field models with a wide range of mass ratios, and a general -field model with a narrow mass spectrum. We uncover that fNL is suppressed as the number of e-foldings grows, and that this suppression is increased in models with a broad spectrum of masses. On the other hand, we find no enhancement to fNL that increases with the number of fields. We thus conclude that the production of a large non-Gaussian signal in multi-field models of inflation is very unlikely as long as fields are slowly rolling and potentials are of simple, quadratic form. Finally, we compute an expression for the scalar spectral index that incorporates the nonlinear corrections to the fields’ evolution.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/694f662941f9160599b9eacede5328dd858e53df

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Xingang Chen
2. C. Byrnes
3. M. Zaldarriaga
4. L. Senatore
5. F. Vernizzi
6. D. Wands
7. Kiwoon Choi
8. D. Seery

In Nuclear and High Energy Physics

1. C. Byrnes
2. L. Senatore
3. Kiwoon Choi
4. M. Zaldarriaga
5. D. Wands
6. F. Vernizzi
7. D. Langlois
8. Xingang Chen

Citations in the corpus

• Primordial Non-Gaussianity (2019, unknown): “[56] Thorsten Battefeld and Richard Easther.”
• Primordial non-Gaussianities from multiple-field inflation (2005, background): “By comparison, our understanding of the multi-field scenario is less developed, although some progress has been made [33]–[38], [18, 19, 14, 15], [39]–[41].”
• The effective field theory of multifield inflation (2010, methodology): “Some related earlier papers that focused on non-Gaussian 3-point and 4-point functions are for example [19, 20, 21, 22, 23, 24, 25].”
• Effects of scale-dependent non-Gaussianity on cosmological structures (2007, unknown): “Contents”
• COrE (Cosmic Origins Explorer) A White Paper (2011, background): “, [100, 101, 102, 103]); models with non-canonical kinetic term [88] (as, e.”
• Non-linear isocurvature perturbations and non-Gaussianities (2008, methodology): “The adiabatic curvature perturbations generated by this model have been computed in [11, 38, 39] and their non-Gaussianity in [40, 41, 42] (see also [43]).”
• Shape of primordial non-Gaussianity and the CMB bispectrum (2008, unknown): “[27] Francis Bernardeau and Jean-Philippe Uzan.”