Bimetric structure formation: non-Gaussian predictions
arXiv:1006.3216 · doi:10.1103/PhysRevD.82.043521
Abstract
The minimal bimetric theory employing a disformal transformation between matter and gravity metrics is known to produce exactly scale-invariant fluctuations. It has a purely equilateral non-Gaussian signal, with an amplitude smaller than that of DBI inflation (with opposite sign) but larger than standard inflation. We consider non-minimal bimetric models, where the coupling appearing in the disformal transformation ${\hat g}_{\mn}= g_{\mn} -B\partial_μϕ\partial_νϕ$ can run with . For power-law these models predict tilted spectra. For each value of the spectral index, a distinctive distortion to the equilateral property can be found. The constraint between this distortion and the spectral index can be seen as a "consistency relation" for non-minimal bimetric models.
17 pages, 2 figures. References and minor comments added in revised version
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