Z(2)XZ(2) ORBIFOLD COMPACTIFICATION AS THE ORIGIN OF REALISTIC FREE FERMIONIC MODELS

I discuss the correspondence between realistic four dimensional free fermionic models and Z2 x Z2 orbifold compactification. I discuss the properties of the Z2 x Z2 orbifold that are reflected in the realistic free fermionic models. I argue that the properties of the realistic free fermionic models arise due to the underlying Z2 X Z2 orbifold compactification with nontrivial background fields. I suggest that three generations is a natural outcome of Z2 x Z2 orbifold compactification with ''standard embedding'' and at the point in compactification space that corresponds to the free fermionic formulation. I discuss how quark flavor mixing is related to the compactification.