A Relation Between N=8 Gauge Theories in Three Dimensions

We show that three-dimensional N=8 $Sp(N)$ and $SO(2N+1)$ gauge theories flow to the same strong coupling fixed point. As a consequence, the corresponding orientifold two-planes in type IIA string theory are described at strong coupling and low-energies by the same M theory background. In the large $N$ limit, these assertions are confirmed by studying discrete torsion in the supergravity theory corresponding to membranes on $R^8\mathrm{/}{Z}_2$.