Inflation after false vacuum decay: Observational prospects after Planck
Abstract
We assess two potential signals of the formation of our universe by the decay of a false vacuum. Negative spatial curvature is one possibility, but the window for its detection is now small. However, another possible signal is a suppression of the cosmic microwave background (CMB) power spectrum at large angles. This arises from the steepening of the effective potential as it interpolates between a flat inflationary plateau and the high barrier separating us from our parent vacuum. We demonstrate that these two effects can be parametrically separated in angular scale. Observationally, the steepening effect appears to be excluded at large ℓ; but it remains consistent with the slight lack of power below ℓ≈30 found by the WMAP and Planck collaborations. We give two simple models which improve the fit to the Planck data; one with observable curvature and one without. Despite cosmic variance, we argue that future CMB polarization and most importantly largescale structure observations should be able to corroborate the Planck anomaly if it is real. If we further assume the specific theoretical setting of a landscape of metastable vacua, as suggested by string theory, we can estimate the probability of seeing a lowℓ suppression in the CMB. There are significant theoretical uncertainties in such calculations, but we argue the probability for a detectable suppression may be as large as O (1 ), and in general is significantly larger than the probability of seeing curvature.
 Publication:

Physical Review D
 Pub Date:
 April 2015
 DOI:
 10.1103/PhysRevD.91.083527
 arXiv:
 arXiv:1309.4060
 Bibcode:
 2015PhRvD..91h3527B
 Keywords:

 98.80.Es;
 98.80.Cq;
 Observational cosmology;
 Particletheory and fieldtheory models of the early Universe;
 High Energy Physics  Theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 34 pages plus appendices, 16 figures. v2: Corrections and clarifications to section 3.2, conclusions unchanged. References added