Relaxion window

Understand

We investigate cosmological constraints on the original relaxion scenario proposed by Graham, Kaplan and Rajendran.

• We first discuss the appropriate sign choice of the terms in the scalar potential, when the QCD axion is the relaxion with a relaxion-inflaton coupling proposed in the original paper.
• We next derive the cosmologically consistent ranges of the mass and a coupling of the relaxion for both the QCD relaxion and non-QCD relaxion.
• The mass range is obtained by $10^{-5}$ eV $\ll m_{\phi} \lesssim 10^4$ eV.