Supersymmetric grand unification in a six-dimensional spacetime

We formulate N=2 supersymmetric GUTs in a six-dimensional spacetime, studying in particular the spontaneous breaking of gauge invariance and the construction of massive gauge multiplets. In six dimensions the photon and gluons are associated with a Weyl photino and Weyl gluinos; the massive W sup(+-), with two Dirac Winos and three spin-O Higgs bosons; the massive Z, with one Dirac Zino and three neutral Higgs bosons. The Xsup(+-4/3) is massless, and the Ysup(+-1/3) has the same mass as the Wsup(+-). The grand-unification mass, generated by the breaking of the 6D Poincare invariance, is associated with the large momenta carried by the grand-unification gauge bosons along the new compact dimensions. (orig.)