entropy per baryon
entropy per baryonA cosmological parameter that measures the relative distribution of energy in disordered and ordered forms in the Universe. It is determined by the number of photons per baryon (proton or neutron) in the Universe today and has a value between 109 and 1010 according to present observations. Big Bang theories must explain the value of this ratio.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006