Speaker
Description
We propose the infrared gauge symmetry of our sector includes an unbroken discrete gauged subgroup of baryon minus lepton number of order $2 \times 3 \text{ colors} \times 3 \text{ generations}$. We UV complete this at a scale $\Lambda$ as the familiar $U(1)_{B-N_cL}$ Abelian Higgs theory, and the early universe phase transition forms cosmic strings which are charged under an emergent higher-form generalized symmetry. These topological defects catalyze interactions which turn $3$ baryons into $3$ leptons at strong scale rates in an analogue of the Callan-Rubakov effect.
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 $\text{SM}+\Lambda\text{CDM}$, and has resisted decades of attempts by cosmologists, nuclear physicists, and astronomers alike to root out systematics. We write down a model in which $B-N_cL$ strings superconduct bosonic global baryon plus lepton number currents and catalyze solely $3p^+ \rightarrow 3e^+$. We suggest that such cosmic strings have disintegrated $\mathcal{O}(1)$ of the lithium nuclei formed during Big Bang Nucleosynthesis and estimate the rate, with our benchmark model finding $\Lambda \sim 10^8 \text{ GeV}$ gives the right number density of strings.
