Unitary IIB Matrix Model and the Dynamical Generation of the Space Time

Abstract

We propose a unitary matrix model as a regularization of the IIB matrix model of Ishibashi-Kawai-Kitazawa-Tsuchiya (IKKT). The fermionic part is incorporated using the overlap formalism in order to avoid unwanted ``doublers'' while preserving the global gauge invariance. This regularization, unlike the one adopted by IKKT, has manifest U(1)^10 symmetry, which corresponds to the ten-dimensional translational invariance of the space time. We calculate one-loop effective action around some typical BPS-saturated configurations in the weak coupling limit. We also discuss a possible scenario for the dynamical generation of the four-dimensional space time through spontaneous breakdown of the U(1)^10 symmetry in the double scaling limit.