  We construct and investigate quantum fields induced on a d-dimensional
dissipationless defect by bulk fields propagating in a (d+1)-dimensional space.
All interactions are localized on the defect. We derive a unitary non-canonical
quantum field theory on the defect, which is analyzed both in the continuum and
on the lattice. The universal critical behavior of the underlying system is
determined. It turns out that the O(N)-symmetric phi^4 theory, induced on the
defect by massless bulk fields, belongs to the universality class of particular
d-dimensional spin models with long-range interactions. On the other hand, in
the presence of bulk mass the critical behavior crossovers to the one of
d-dimensional spin models with short-range interactions.
