Tuesday 9 January 2018

cosmology - Baryon / photon ratio


The key parameter which determines the abundances of light elements is the baryon/photon ratio. Is this ratio derived from first principles -if so, how- or, if it results from a small favoritism for matter over antimatter in the early universe, then from what observations is the baryon/photon ratio calculated -and how? Though the early universe is assumed to be dominated by radiation, how do we know this? Is it because we need this radiation to explain its evolution, i.e., the observed abundances? As far as I’m aware of, this radiation cannot be observed as the universe at that time was opaque.




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