4D models of Scherk-Schwarz GUT breaking via deconstruction -: art. no. 015004

We examine new classes of GUT models where the GUT gauge group is broken by a 4D analogue of the Scherk-Schwarz mechanism. These models are inspired by "deconstructed" 5D Scherk-Schwarz orbifold models. However, no fine-tuning of parameters or assumption of higher dimensional Lorentz invariance is necessary, and the number of lattice sites can be as low as just two. These models provide simple ways to solve the doublet-triplet splitting problem, change proton decay predictions, and may provide insight into the structure of the CKM matrix. Since the number of fields in these models is finite, the corrections to the unification of gauge couplings can be reliably calculated, and as expected result only in threshold corrections to the differential running of the couplings. Our analysis also suggests new 4D models which can enjoy the benefits of orbifold models but cannot be obtained by deconstruction of a 5D model.