Axions as Topological Inflatons and Geometric Curvatons

by Tommy on 5/05/2017
Axion Phase Diagram

Axion Phase Diagram

Back just before the first of the year I was deep into writing up my gravitational axion hypothesis. This was precipitated by new precision observational results demonstrating their particulate nature convincingly. The debate was raging between entropic gravity and fundamental particles, and to a lesser degree a wide variety of quite unreasonable proposals, and I was trying to get something together because I knew Vera Rubin was failing and the debate was reaching truly ridiculous and embarrassing proportions. Just as I was getting started, this paper showed up on the Arxiv. I already had a profound respect for SISSA, since their astronomy was crucial to the precision astronomical debates. So I was really happy to read this paper and blogged it briefly, but over the next week I was engaged in writing up my hypothesis and simply forgot all about it.

Since this has now been published in Physical Review Letters, it’s worth reviewing it here again.

Geometric Baryogenesis from Shift Symmetry, Andrea De Simone, Takeshi Kobayashi and Stefano Liberati, Phys. Rev. Lett. 118, 131101 (27 March 2017), doi:10.1103/PhysRevLett.118.131101

We present a new scenario for generating the baryon asymmetry of the universe that is induced by a Nambu-Goldstone (NG) boson. The shift symmetry naturally controls the operators in the theory, while allowing the NG boson to couple to the spacetime geometry. The cosmological background thus sources a coherent motion of the NG boson, which leads to baryogenesis. Good candidates of the baryon-generating NG boson are the QCD axion and axion-like fields. In these cases the axion induces baryogenesis in the early universe, and can also serve as dark matter in the late universe.

So this paper takes modern axion cosmological model building and then runs with it.

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