Speaker
Description
What happens when a charged chiral fermion interacts with a monopole? This fundamental question has arisen within the standard model. Callan discovered that what bounces back is not the original fermion but rather a particle that sometimes has a fractional charge, suggesting a fraction of electrons. This paradox, known as the "monopole paradox," has long posed interpretative challenges. Recently, a series of works have made progress on this topic, showing that the scattered particle can be viewed as a chiral fermion dressed with a topological string attached to the monopole. This string brings the fermion into the twisted sector, resulting in a fractional charge. This serves as a compelling example in field theory. But what about on the lattice?
In this talk, I will introduce analogous cases in condensed matter physics. When a pair of dual theories is coupled, we can design the interaction at the interface that exhibits perfect transmission for any wave packet. The particle that passes through the interface appears quite different from the original, as it is essentially disguised by a topological line. I will demonstrate a generic yet straightforward method to construct these models using matrix product unitaries and conclude by discussing the implications for some applications and the monopole paradox.