4-D Quantum Dilaton Gravity During Inflation and Renormalization at One loop

We consider 4D quantum-dilaton gravity with the most general coupling in a homogeneous and isotropic universe, especially an inflationary one, which is essentially characterized by an exponentially expanding scale factor with time. We show that on the inflationary background this theory can be miraculously renormalized, at least at the one-loop level, which must be an effective theory during the inflation of the un-constructed complete quantum theory of gravity.Comment: 18 pages, latex, no figures. This paper also available at http://theory.kek.jp/~takata/mypaper/paper.html#mypaper5.p

One loop renormalization of the 4-D Quantum Dilaton Gravity in Spherical symmetric background

We study the one loop renormalization in the most general metric-dilaton theory with second derivative only. In constant background dilaton theory, there are two types of gravity background which enable the theory renormalizable at one-loop level. We show this concretely to discuss on the spherical symmetric background.Comment: 7 pages, latex, no figures. This paper also available at HUPD-960

Interaction between two Fuzzy Spheres

We have calculated interactions between two fuzzy spheres in 3 dimension. It depends on the distance r between the spheres and the radii rho_1, rho_2. There is no force between the spheres when they are far from each other (long distance case). We have also studied the interaction for r=0 case. We find that an attractive force exists between two fuzzy sphere surfaces.Comment: Latex file, 13 page

Maxwell Theory from Matrix Model

We present a scenario for deriving Maxwell theory from IIB matrix model. Four dimensional spacetime and theories on it relate different dimensional ones by applying appropriate limits of the backgrounds of matrix model. It is understood by looking at open strings bits as bi-local fields on the spacetime, which are decoupled from the bulk in the limits. The origin of electric-magnetic duality is also discussed in matrix model.Comment: Lattice 2000 (Gravity and Matrix Models), 4 page