Blue tensor spectrum from particle production during inflation

Shinji Mukohyama, Ryo Namba, Marco Peloso, Gary Shiu

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63 Scopus citations


We discuss a mechanism of particle production during inflation that can result in a blue gravitational wave (GW) spectrum, compatible with the BICEP2 result and with the r < 0.11 limit on the tensor-to-scalar ratio at the Planck pivot scale. The mechanism is based on the production of vector quanta from a rolling pseudo-scalar field. Both the vector and the pseudo-scalar are only gravitationally coupled to the inflaton, to keep the production of inflaton quanta at an unobservable level (the overproduction of non-gaussian scalar perturbations is a generic difficulty for mechanisms that aim to generate a visible GW signal from particle production during inflation). This mechanism can produce a detectable amount of GWs for any inflationary energy scale. The produced GWs are chiral and non-gaussian; both these aspects can be tested with large-scale polarization data (starting from Planck). We study how to reconstruct the pseudo-scalar potential from the GW spectrum.

Original languageEnglish (US)
Article number036
JournalJournal of Cosmology and Astroparticle Physics
Issue number8
StatePublished - Aug 1 2014


  • gravitational waves and CMBR polarization
  • inflation
  • primordial gravitational waves (theory)


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