1:30 pm MCP 201
Lightlike conformal line defects should appear in a number of places in theoretical physics, from null Wilson lines, to impurities moving at the speed of sound in a material, and as exponentials of light-ray/detector operators. Surprisingly, little is known about their existence and correlation functions.
In this talk, I will discuss some initial steps towards understanding null line defects in Lorentzian CFTs. First, I will describe their large symmetry algebra (larger than timelike/spacelike counterparts) and general constraints on Ward identities. Then I will study the (3+1)d free scalar pinning field example in detail. Physical consistency conditions compel us to consider distributional subtleties of correlation functions in Lorentzian signature, making ultraboosted limits sensible and unambiguous, making symmetries match expectations, and modifying conformal anomalies. Applying these lessons to a massless charged particle in pure Maxwell theory, we understand symmetry breaking by null Wilson lines and obtain a resolution to the longstanding problem of ultrarelativistic limits of gauge potentials in classical E&M.