  Explicit supersymmetry breaking is studied in higher dimensional theories by
having boundaries respect only a subgroup of the bulk symmetry. If the boundary
symmetry is the maximal subgroup allowed by the boundary conditions imposed on
the fields, then the symmetry can be consistently gauged; otherwise gauging
leads to an inconsistent theory. In a warped fifth dimension, an explicit
breaking of all bulk supersymmetries by the boundaries is found to be
inconsistent with gauging; unlike the case of flat 5D, complete supersymmetry
breaking by boundary conditions is not consistent with supergravity. Despite
this result, the low energy effective theory resulting from boundary
supersymmetry breaking becomes consistent in the limit where gravity decouples,
and such models are explored in the hope that some way of successfully
incorporating gravity can be found. A warped constrained standard model leads
to a theory with one Higgs boson with mass expected close to the experimental
limit. A unified theory in a warped fifth dimension is studied with boundary
breaking of both SU(5) gauge symmetry and supersymmetry. The usual
supersymmetric prediction for gauge coupling unification holds even though the
TeV spectrum is quite unlike the MSSM. Such a theory may unify matter and Higgs
in the same SU(5) hypermultiplet.
