Redundancies in Explicitly Constructed Ten Dimensional Heterotic String   Models
  Using Baylor University's C++ software for construction of weakly coupled free fermionic heterotic string models, called the FF Framework, we explicitly construct the level 1 Ka\v{c}-Moody ten dimensional heterotic string models with the aim of understanding the redundancies endemic to this construction method. We show that for models in any even number of large space-time dimensions with a massless left mover and an odd ordered right mover, the maximal number of space-time supersymmetries are present. We show that in order to produce all of the models for a given order, different basis vectors must be built; one cannot vary only the GSO coefficients. We also show that all combinations of two order-2 basis vectors do not produce the same models as all possible single order-4 basis vectors, implying the product of the orders used in a search does not necessarily determine the models built. We also show that to build all of the D=10 level-1 models the inputs must be: sets of single order-6 basis vectors, pairs of basis vectors with orders 3 and 2, or sets of three order-2 basis vectors. 
Timothy Renner, Jared Greenwald, Douglas Moore, Gerald Cleaver
hep-ph hep-th