Supersymmetric coset unified theories: Susy guts

I consider the possibility that the observed quarks and leptons (and their N = 1 SUSY partners) live in a Kahler coset space G/H with H ^e SU(3) × SU(2) × U(1). This uniquely points towards an appropriate complex (non-compact) extension of the coset space E₇/SU(3) × SU(2) × U(1)⁴ in which there is room for three usual chiral families plus a fourth ``mirror'' family. The SU(5) subgroup of E<sub>7</sub> may by gauged to give the GUT of Georgi and Glashow which is spontaneously broken down to the standard model. The Kahler manifold may in principle be coupled to N = 1 supergravity originating a realistic ``SUGRA GUT''. It is finally speculated about the origin of the hierarchy of quark and lepton masses which is suggested to be connected to a possible ``tumbled'' structure of the manifold.