Matrix models in homogeneous spaces

We investigate noncommutative gauge theories in homogeneous spaces G/H. We construct such theories by adding cubic terms to IIB matrix model which contain the structure constants of G. The isometry of a homogeneous space, G must be a subgroup of SO(10) in our construction. We investigate CP2 = SU(3)/U(2) case in detail which gives rise to 4-dimensional noncommutative gauge theory. We show that noncommutative gauge theory on R-4 can be realized in the large-N limit by letting the action approach IIB matrix modelin a definite way. We discuss possible relevances of these theories to the large-N limit of IIB matrix model. (C) 2002 Elsevier Science B.V. All rights reserved.