Abstract
Within the standard big bang nucleosynthesis (BBN) and cosmic microwave background (CMB) framework, the baryon density measured by the Wilkinson Microwave Anisotropy Probe (WMAP) or the primordial D abundance is much higher than the one measured by the 7Li abundance. We propose two non‐standard cosmological scenarios to solve the discrepancy. In the first scenario, we consider BBN with non‐standard values of the fine structure constant and/or the cosmic expansion rate. We show that the discrepancy is not solved by considering either a varying fine structure constant or a non‐standard expansion rate alone but solutions are found by their simultaneous existence. In the second scenario, we consider additional baryons which appear after BBN. We show that simply adding the baryons can not be a solution but the existence of a large lepton asymmetry before BBN makes the scenario successful. These extra baryons and leptons, in addition to the initial baryons which exist before the BBN, can be all produced from Q‐balls.
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