An Orbifold of Type 0B Strings and Non-supersymmetric Gauge Theories

We study a ${\text{IZ}}_2$ orbifold of Type 0B string theory by reflection of six of the coordinates (this theory may also be thought of as a ${\text{IZ}}_4$ orbifold of Type IIB string theory by a rotation by $\pi$ in three independent planes). We show that the only massless mode localized on the fixed fourplane ${\text{IR}}^{3,1}$ is a U(1) gauge field. After introducing D3-branes parallel to the fixed fourplane we find non-supersymmetric non-abelian gauge theories on their worldvolume. One of our results is that the theory on equal numbers of electric and magnetic D3-branes placed at the fourplane is the ${\text{IZ}}_4$ orbifold of $\mathcal{N}=4$ supersymmetric Yang-Mills theory by the center of its R-symmetry group.