A Density Spike on Astrophysical Scales from an N-Field Waterfall Transition
Oct 7, 2014
12 pages
Published in:
- Phys.Lett.B 748 (2015) 132-143
- Published: Jul 2, 2015
e-Print:
- 1410.1878 [astro-ph.CO]
Report number:
- MIT-CTP-4499
Citations per year
Abstract: (Elsevier)
Hybrid inflation models are especially interesting as they lead to a spike in the density power spectrum on small scales, compared to the CMB, while also satisfying current bounds on tensor modes. Here we study hybrid inflation with N waterfall fields sharing a global SO(N) symmetry. The inclusion of many waterfall fields has the obvious advantage of avoiding topologically stable defects for N>3 . We find that it also has another advantage: it is easier to engineer models that can simultaneously (i) be compatible with constraints on the primordial spectral index, which tends to otherwise disfavor hybrid models, and (ii) produce a spike on astrophysically large length scales. The latter may have significant consequences, possibly seeding the formation of astrophysically large black holes. We calculate correlation functions of the time-delay, a measure of density perturbations, produced by the waterfall fields, as a convergent power series in both 1/N and the field's correlation function Δ(x) . We show that for large N , the two-point function is 〈δt(x)δt(0)〉∝Δ2(|x|)/N and the three-point function is 〈δt(x)δt(y)δt(0)〉∝Δ(|x−y|)Δ(|x|)Δ(|y|)/N2 . In accordance with the central limit theorem, the density perturbations on the scale of the spike are Gaussian for large N and non-Gaussian for small N .Note:
- 15 pages in double column format, 6 figures. V2: Further clarifications, updated to coincide with version published in Physics Letters B
- density: perturbation
- inflation: hybrid
- power spectrum: density
- model: hybrid
- inflation: model
- power spectrum: primordial
- defect: stability
- n-point function: 3
- correlation function
- cosmic background radiation
References(62)
Figures(7)
- [1]
- [2]
- [3]
- [4]
- [5]
- [6]
- [7]
- [8]
- [9]
- [10]
- [11]
- [12]
- [13]
- [14]
- [15]
- [16]
- [17]
- [18]
- [19]
- [20]
- [21]
- [22]
- [23]
- [24]
- [25]