Abstract
We present a scenario where an axion-like field drives inflation until a potential barrier, which keeps a waterfall field at the origin, disappears and a waterfall transition occurs. Such a barrier separates the scale of inflation from that of the waterfall transition. We find the observed spectrum of the cosmic microwave background indicates that the decay constant of the inflaton is well below the Planck scale, with the inflationary Hubble parameter spanning a wide range. Further, our model involves dark matter candidates including the inflaton itself. Also, for a complex waterfall field, we can determine cosmologically the Peccei-Quinn scale associated with the strong CP problem.
Highlights
Cosmic inflation [1,2,3] has become an essential part of the standard cosmological model
The waterfall field remains at the origin by a potential barrier, which disappears when the inflaton reaches at a critical point— inflation ends almost instantaneously
The inflaton interaction responsible for such a barrier can naturally arise if the shift symmetry is broken nonperturbatively by hidden QCD with quarks coupled to the waterfall field
Summary
Cosmic inflation [1,2,3] has become an essential part of the standard cosmological model. Before the onset of the hot big bang evolution, it provides the necessary initial conditions—otherwise extremely finely tuned—as confirmed by the observations on the cosmic microwave background (CMB) [4] It explains the origin of temperature fluctuations of the CMB and the inhomogeneous distribution of galaxies on large scales due to quantum fluctuations during inflation [5]. Unlike the original natural inflation, the inflaton is allowed to have a decay constant well below mPl so that the effective field theory is trustable, yet maintains a flat potential. The Planck results are accommodated in a broad range of the inflaton mass and decay constant, but with a certain relationship between them This opens an interesting possibility to probe inflation via experimental searches for axionlike particles.
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