The corona poling process of electro-optic polymers has been investigated for rodlike aromatic polyimides doped with nonlinear optical chromophores. The dynamics of the chromophores in poling during and after imidization was observed by measuring second harmonic generation (SHG) from the polymer. In the course of poling during imidization, the SHG, observed before imidization, decreases to zero, reappears, and increases as the temperature increases. When poling was after imidization, the SHG intensity increased monotonically with increasing temperature. The disappearance of SHG in the poling during imidization is probably due to the known structural change in the polymer chains during imidization and the subsequent reorientation of the chromophores caused by formation of sheets of polyimides. The characteristics of the samples poled during and after imidization are nearly the same in both the extent of the nonlinear susceptibility and their thermal stability.

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A 6-dimensional grand unified theory with the compact space having the topology of a real projective plane, i.e., a 2-sphere with opposite points identified, is considered. The space is locally flat except for two conical singularities where the curvature is concentrated. One supersymmetry is preserved in the effective 4d theory. The unified gauge symmetry, for example SU(5) , is broken only by the non-trivial global topology. In contrast to the Hosotani mechanism, no adjoint Wilson-line modulus associated with this breaking appears. Since, locally, SU(5) remains a good symmetry everywhere, no UV-sensitive threshold corrections arise and SU(5)-violating local operators are forbidden. Doublettriplet splitting can be addressed in the context of a 6d N = 2 super Yang-Mills theory with gauge group SU(6). If this symmetry is first broken to SU(5) at a fixed point and then further reduced to the standard model group in the above non-local way, the two light Higgs doublets of the MSSM are predicted by the group-theoretical and geometrical structure of the model.