Orientifolded matrices and supersymmetries that give rise to spacetime directional asymmetry of effective interactions

Effects of matrix orientifolding that preserves supersymmetries are considered in the IIB matrix model with regard to its effective dynamics generated for diagonal elements. Taking the case of maximal supersymmetries and the long distance expansion of the one-loop effective action as well as cases where the size of the matrices is small, we demonstrate that the directional asymmetry of spacetime brought upon by this setup in fact leads to that of the forces exerting on the spacetime points: in addition to the two-body attraction between two points, there are attractions toward the four-dimensional plate.