Anomalous U(1) GUT

We have proposed a very attractive scenario of Grand Unified Theories (GUTs). It employs the supersymmetry (SUSY) and an anomalous U(1) symmetry whose anomaly is canceled via the Green-Schwarz mechanism. In this scenario, the doublet-triplet splitting problem is solved and the success of the gauge coupling unification in the minimal SU(5) GUT is naturally explained with sufficiently stable nucleon. Realistic fermion Yukawa matrices can also be realized simultaneously. In addition, a horizontal symmetry helps to solve the SUSY-flavor problem.