PRODUCTION OF HEAVY-ELEMENTS IN INHOMOGENEOUS COSMOLOGIES

Baryon density inhomogeneities during big bang nucleosynthesis can res ult from a variety of possible causes (e.g., quantum chromodynamic and electroweak phase transitions; cosmic strings). We present here the c onsequences of such inhomogeneities with special emphasis on the produ ction of heavy elements in a parameter study, varying the global baryo n-to-photon ratio eta [which is related to the baryon density and the Hubble constant via eta10 = 64.94OMEGA(b)(H-0/50)2] and the length sca le of the density inhomogeneities. The production of heavy elements be yond Fe can only occur in neutron-rich environments; thus, we limit ou r study to neutron-rich zones, originating from neutron diffusion into low-density regions. In this first calculation including elements hea vier than Si, we prove an earlier hypothesis that under such condition s r-process elements can be produced, strongly enhanced by the process of fission cycling. Primordial r-process abundances are, however, ver y sensitive to the choice of eta. Significant amounts, comparable to o r larger than the (permitted) floor of heavy-element abundances found in low-metallicity stars at the onset of galactic evolution, can only be obtained for values in excess of eta10 = 133 (i.e., OMEGA(b)h50(2) = 2.0; e.g., OMEGA(b) = 1, H-0 = 71 or OMEGA(b) = 0.5, H-0 = 100) and large length scales of inhomogeneities, which minimize the back-diffus ion of neutrons into proton-rich regions. Recent investigations analyz ing the primordial abundances of light elements seem to set tighter li mits, eta10 < 26-39 (OMEGA(b)h50(2) < 0.4-0.6), from He-4 and apparent ly considerably lower values based on Li, Be, and B. Under such condit ions the predicted abundances of heavy elements are a factor of 10(5) or more below presently observable limits.