1:30 pm MCP 201
A Cosmological Lithium Solution.
The cosmological lithium problem---that the observed primordial abundance is lower than theoretical expectations by a factor of a few---is perhaps the most statistically significant anomaly of SM + ΛCDM, and has resisted decades of attempts by cosmologists, nuclear physicists, and astronomers alike to root out systematics. Beginning with the conspiratorial observation that the atomic number of lithium matches the number of particle generations Ng, we uncover a surprisingly close link to fundamental physics.
We gauge baryon minus lepton number and spontaneously break it in the early universe to a discrete subgroup, whereupon cosmic strings form. With a nonminimal breaking which respects the SM anomaly-free discrete global symmetries, such topological defects catalyze interactions which turn Ng protons into Ng positrons at strong scale rates in an analogue of the Callan-Rubakov effect. We propose that such cosmic strings have disintegrated the lithium nuclei formed during Big Bang Nucleosynthesis, lay out the phenomenology of this model, and estimate the rates possible to demonstrate its cosmic relevance.