1 Big Bang Nucleosynthesis and Primordial Black Holes

Abstract: There are ongoing efforts in detecting Hawking radiation from primordial black holes (PBH) formed during the early universe. Here we put an upper limit on the PBH number density that could have been formed prior to the big bang nucleosynthesis era, based on the constraint that the PBH evaporation energy consisting of high energy radiation not affect the observed abundances ’ of elements, by disintegrating the nuclei. This puts a limit of 1510 PBH The light elements in the universe were made in the big bang nucleosynthesis (BBN) in the first 3 minutes when temperature was ~10 9 K. The synthesis of these elements as the hot universe expands is predicted by the theory which matches with observations [1]. That is 245.0 abundance for hydrogen, ~10-5 of deuterium and He3 and ~10-9 of Li7. Beyond three minutes, the temperature became too low for the synthesis of any higher elements beyond Li