We study the supersymmetric GUT models where the supersymmetry and GUT gauge symmetry can be broken by the discrete symmetry. First, with the ansatz that there exist discrete symmetries in the branes’ neighborhoods, we discuss the general reflection Z2 symmetries and GUT breaking on M 4 × M1 and M4 × M1 × M1. In those models, the extra dimensions can be large and the KK states can be set arbitr...

We discuss why the SU(3) supersymmetric model with the most general superpotential can naturally break to the standard model if gauge singlets and a discrete symmetry are included. This mechanism does away with the need for fine-tuning in the form of the assumed absence of certain terms in the superpotential. It also automatically guarantees that any abelian discrete phase symmetry of the GUT w...

In the minimal supersymmetric Standard Model with seesaw neutrino masses we show how R–parity can emerge naturally as a discrete gauge symmetry. The same discrete symmetry explains the smallness of the μ–term (the Higgsino mass parameter) via the Giudice–Masiero mechanism. The discrete gauge anomalies are cancelled by a discrete version of the Green–Schwarz mechanism. The simplest symmetry grou...