  Quantum criticality in systems of local moments interacting with itinerant
electrons has become an important and diverse field of research. Here we review
recent results which concern (a) quantum phase transitions in single-impurity
Kondo and Anderson models and (b) quantum phase transitions in heavy-fermion
lattice models which involve critical quasiparticles. For (a) the focus will be
on impurity models with a pseudogapped host density of states and their
applications, e.g., in graphene and other Dirac materials, while (b) is devoted
to strong-coupling behavior near antiferromagnetic quantum phase transitions,
with potential applications in a variety of heavy-fermion metals.
