  The matrix model formulation of M theory can be generalized to compact
transverse backgrounds such as tori. If the number of compact directions is K
then the matrix model must be generalized to K+1 dimensional super Yang Mills
theory on a compact space. If K is greater than or equal to 3, there are T
dualities which which require highly nontrivial identifications between
different SYM theories. In the simplest case we will see that the requirement
reduces to the well known electric- magnetic duality of N=4 SYM theory in 3+1
dimensions.
