Speaker: Gonzalo Alonso

Abstract:  Axion-like particles that couple to QCD via a G∧G term can induce a dependence of the mass of the proton and the neutron on the value of the axion field. It has been argued that an axion that couples too strongly to QCD results in the
underproduction of 4He during Big Bang Nucleosynthesis (BBN), which sets bounds on the allowed mass and decay constant of the axion. However, this very same effect results in a temperature-dependent effective potential for the axion in the presence of a background density of baryons, as there was in the early universe. Studying this effective potential leads to a deviation in the cosmological evolution of the axion field that can affect the BBN bounds. 

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