Abstract
We present an intrinsic leptogenesis mechanism in models of axion inflation with a classical SU(2) gauge field. The gauge field is coupled to the axion with a Chern-Simons interaction and comprises a tiny fraction of the total energy, ρYM/ρtot ≲ ϵ2. However, it has spin-2 fluctuations which breaks the parity and leads to the generation of chiral gravitational waves during inflation. By the gravitational anomaly in SM, it naturally creates a net lepton number density, sufficient to explain the matter asymmetry. We show that this mechanism can generate the observed value of baryon to photon number density in a natural range of parameters and yet has a small chiral tensor power spectrum on large scales.
Highlights
In [15], we studied the cosmic perturbations in a generic axion inflation model with a small SU(2) gauge field1
Our central finding was the existence of a parameter regime in which the gauge field can simultaneously generate a detectable chiral gravitational wave signal and has a negligible contribution to the scalar fluctuations, in agreement with the current CMB observations
The perturbed gauge field has a spin-2 fluctuation which linearly coupled to the primordial gravitational waves and explicitly breaks the parity between its left- and right-handed polarizations
Summary
The fluctuations of the SU(2) gauge field contributes to the cosmic perturbations and leads to new theoretical and observational features. Where γij is the gravitational wave and δT denotes the tensor sector of the fluctuations. Perturbing the SU(2) gauge field around its isotropic configuration (2.6), we have another tensor fluctuation, γij, given as. The Yang-Mills term in the action generates an anisotropic inertia in the linear order energy-momentum tensor πiTj. We emphasis that in order to have a linear order anisotropic inertia in (3.3), the gauge fields should be turned on at the background level (ψ = 0). Going to the Fourier space, we can diagonalize the system of (3.4) and (A.3) in terms of circular polarization modes. We can expand γij and γij in terms of the right- and left-handed polarization states γij(τ, x).
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