A Gapless Hard Wall: Magnetic Catalysis in Bulk and Boundary

Understand

We study various aspects of fermions and their chiral condensates, both in the bulk of AdS4 spacetime and in the dual boundary theory.

• For the most part, we focus on a geometry with an infra-red hard wall.
• We show that, contrary to common lore, there exist boundary conditions in which the hard wall gives rise to a discrete, but gapless, fermionic spectrum.
• In such a setting, the presence of a magnetic field induces a bulk fermion condensate which spontaneously breaks CP invariance.