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Learn about cosmic strings and their potential role in solving the cosmological lithium problem through this physics lecture from the Workshop on Phase Transitions and Topological Defects in the Early Universe. Explore how the baryon minus lepton number gauge theory, when broken by a scalar with charge six, leads to cosmic string solutions that may explain why observed primordial lithium abundance is only one-third of theoretical predictions. Discover how these topological defects can facilitate proton-to-positron conversion through an amplified strong-scale cross-section mechanism similar to the Callan-Rubakov effect. Examine the first proposed new physics mechanism with microphysical justification for specifically modifying lithium abundance after Big Bang Nucleosynthesis, potentially resolving a decades-old puzzle that has challenged cosmologists, nuclear physicists, and astronomers.
