Adam Chalabi (NBI), Boundaries in free higher-derivative conformal field theories

Tuesday 18 Apr 2023, 14:00 → 15:30 Europe/Stockholm

Albano 3: 6228 - Mega (22 seats) (Albano Building 3)

Free higher-derivative theories are simple yet non-trivial conformal field theories (CFTs). Their actions contain higher-order kinetic terms, leading to features that high-energy theorists may find unusual, such as an unbounded Hamiltonian and loss of unitarity. Nonetheless, these theories are useful toy models, e.g. for quantum gravity, and have found real-world applications, e.g. in the theory of elasticity. In this talk, I will describe the effects arising from the presence of a boundary in such theories. Concretely, I will discuss free scalar and free Dirac fermion higher-derivative theories, and determine the space of conformal boundary conditions. I will show how a rich picture of boundary renormalisation group flows between them emerges. Finally, I will summarise a number of computations of boundary CFT data. These reveal some of the strange features of these boundary CFTs, and e.g. demonstrate that the boundary a-theorem does not hold.