5 research outputs found
Constraints on small-field axion inflation
We study general class of small-field axion inflations which are the mixture
of polynomial and sinusoidal functions suggested by the natural and axion
monodromy inflations. The axion decay constants leading to the successful axion
inflations are severely constrained in order not to spoil the Big-Bang
nucleosynthesis and overproduce the isocurvature perturbation originating from
the QCD axion. We in turn find that the cosmologically favorable axion decay
constants are typically of order the grand unification scale or the string
scale which is consistent with the prediction of closed string axions.Comment: 17 pages, 6 figures; v2 published versio
Modulus D-term Inflation
We propose a new model of single-field D-term inflation in supergravity,
where the inflation is driven by a single modulus field which transforms
non-linearly under the U(1) gauge symmetry. One of the notable features of our
modulus D-term inflation scenario is that the global U(1) remains unbroken in
the vacuum and hence our model is not plagued by the cosmic string problem
which can exclude most of the conventional D-term inflation models proposed so
far due to the CMB observations.Comment: 15 pages, 5 figure