  The IIB matrix model is one of the candidates for nonperturbative formulation
of string theory, and it is believed that the model contains gravitational
degrees of freedom in some manner. In some preceding works, it was proposed
that the matrix model describes the curved space where the matrices represent
differential operators that are defined on a principal bundle. In this paper,
we study the dynamics of the model in this interpretation, and point out the
necessity of the principal bundle from the viewpoint of the stability and
diffeomorphism invariance. We also compute the one-loop correction which
possibly yields a mass term for each field due to the principal bundle. We find
that the correction does generate some mass terms with the supersymmetry
broken, while fields in the original IIB matrix model remain massless. The
positivity is not violated as long as the number of bosonic degrees of freedom
is larger than the fermionic counterpart. The generation of mass terms means
that the new mass scale emerges through the loop correction.
