Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 6, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2013/06/013
Keywords
physics of the early universe; cosmological parameters from CMBR; cosmology of theories beyond the SM; cosmological perturbation theory
Funding
- World Premier International Center Initiative (WPI Program), MEXT, Japan
- [24111702]
- [21111006]
- [23104008]
- [22244030]
- [21244033]
- [24740135]
- Grants-in-Aid for Scientific Research [22244030] Funding Source: KAKEN
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We show that a sizable running spectral index suggested by the recent SPT data can be explained in the axionic curvaton model with a potential that consists of two sinusoidal contributions of different height and period. We find that the running spectral index is generically given by dn(s)/dln k similar to 2 pi/Delta N(n(s) - 1), where Delta N is the e-folds during one period of modulations. In the string axiverse, axions naturally acquire a mass from multiple contributions, and one of the axions may be responsible for the density perturbations with a sizable running spectral index via the curvaton mechanism. We note that the axionic curvaton model with modulations can also accommodate the red-tilted spectrum with a negligible running, without relying on large-field inflation.
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