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Sound Speed of Primordial Fluctuations in Supergravity Inflation
- Source :
- Phys. Rev. Lett. 117, 101301 (2016)
- Publication Year :
- 2016
-
Abstract
- We study the realization of slow-roll inflation in $\mathcal N = 1$ supergravities where inflation is the result of the evolution of a single chiral field. When there is only one flat direction in field space, it is possible to derive a single-field effective field theory parametrized by the sound speed $c_s$ at which curvature perturbations propagate during inflation. The value of $c_s$ is determined by the rate of bend of the inflationary path resulting from the shape of the $F$-term potential. We show that $c_s$ must respect an inequality that involves the curvature tensor of the Kahler manifold underlying supergravity, and the ratio $M/H$ between the mass $M$ of fluctuations ortogonal to the inflationary path, and the Hubble expansion rate $H$. This inequality provides a powerful link between observational constraints on primordial non-Gaussianity and information about the $\mathcal N = 1$ supergravity responsible for inflation. In particular, the inequality does not allow for suppressed values of $c_s$ (values smaller than $c_s \sim 0.4$) unless (a) the ratio $M/H$ is of order 1 or smaller, and (b) the fluctuations of mass $M$ affect the propagation of curvature perturbations by inducing on them a nonlinear dispersion relation during horizon crossing. Therefore, if large non-Gaussianity is observed, supergravity models of inflation would be severely constrained.<br />Comment: 6 pages, 2 figures; v2: references added, improved discussion; v3: typos corrected, version published in PRL
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. Lett. 117, 101301 (2016)
- Publication Type :
- Report
- Accession number :
- edsarx.1601.05457
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevLett.117.101301