  Electronic states at domain walls in bilayer graphene are studied by
analyzing their four and two band continuum models, by performing numerical
calculations on the lattice, and by using quantum geometric arguments. The
continuum theories explain the distinct electronic properties of boundary modes
localized near domain walls formed by interlayer electric field reversal, by
interlayer stacking reversal, and by simultaneous reversal of both quantities.
Boundary mode properties are related to topological transitions and gap
closures which occur in the bulk Hamiltonian parameter space. The important
role played by intervalley coupling effects not directly captured by the
continuum model is addressed using lattice calculations for specific domain
wall structures.
