Entropy Production at the Bounce and the Dilution of an Earlier Asymmetry

If a bounce releases entropy, every relic abundance produced beforehand is diluted by the same factor, and the baryon asymmetry is no exception. This paper computes how much entropy production a pre-bounce asymmetry can survive. With the yield from any mechanism bounded by Y_pre <= epsilon/g_star <= 9.37e-03 for CP asymmetry at most unity, and the required final yield fixed at 8.69e-11, the largest tolerable entropy factor is Delta = 1.08e+08. A factor of 100 already demands a pre-bounce yield of 8.69e-09; an initial yield of 1e-8 emerges as 1.00e-09 after a factor of ten and as 1.00e-11 after a factor of a thousand, the latter well below the observed value. Bounces with entropy factors above about 1e5 therefore erase any plausible pre-bounce asymmetry and force baryogenesis to occur on the expanding side. Computed from stated assumptions, not measured.