We investigate the possibility of accounting for the currently inferred primordial abundances of D , ^ { 3 } He , ^ { 4 } He , and ^ { 7 } Li by big bang nucleosynthesis in the presence of baryon density inhomogeneities plus the effects of late–decaying massive particles ( X ) , and we explore the allowed range of baryonic fraction of the closure density \Omega _ { b } in such context .
We find that , depending on the parameters of this composite model ( characteristic size and density contrast of the inhomogeneities ; mass–density , lifetime , and effective baryon number in the decay of the X particles ) , values as high as \Omega _ { b } h _ { 50 } ^ { 2 } \simeq 0.25 - 0.35 could be compatible with the primordial abundances of the light nuclides .
We include diffusion of neutrons and protons at all stages , and we consider the contribution of the X particles to the energy density , the entropy production by their decay , the possibility that the X–products could photodissociate the light nuclei produced during the previous stages of nucleosynthesis , and also the possibility that the decay products of the X–particles would include a substantial fraction of hadrons .
Specific predictions for the primordial abundance of Be are made .