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arXiv · 1702.07689

Gauss-Bonnet Chern-Simons gravitational wave leptogenesis

Shinsuke Kawai·Jinsu Kim
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Abstract

The gravitational Chern-Simons term coupled to an evolving axion is known to generate lepton number through the gravitational anomaly. We examine this leptogenesis scenario in the presence of the Gauss-Bonnet term over and above the gravitational Chern-Simons term. We find that the lepton production can be exponentially enhanced. The Gauss-Bonnet term creates CP-violating instability of gravitational waves that may appear transiently after inflation, and during the period of instability elliptically polarized gravitational waves are exponentially amplified at sub-horizon scales. This instability does not affect the spectrum of the cosmic microwave background as it occurs at much shorter length scales. In a typical scenario based on natural inflation, the observed baryon asymmetry of the Universe corresponds to the UV cutoff scale at $10^{14-16}$ GeV.

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Shinsuke Kawai, Jinsu Kim. 2017-02-24. Gauss-Bonnet Chern-Simons gravitational wave leptogenesis. https://doi.org/10.1016/j.physletb.2018.12.019

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