New results on γ_(rm str) in 2D quantum gravity using Regge calculus

We study 2D quantum gravity on spherical topologies using the Regge calculus approach. Our goal is to shed new light upon the validity of the Regge approach to quantum gravity, which has recently been questioned in the literature. We incorporate an $R^2$ interaction term and investigate its effect on the value of the string susceptibility exponent $\gamma_{\rm str}$ using two different finite-size scaling Ans\"atze. Our results suggest severe shortcomings of the methods used so far to determine $\GS$ and show a possible cure of the problems. To have better control over the influence of irregular vertices, we choose besides the almost regular triangulation of the sphere as the surface of a cube a random triangulation according to the Voronoi-Delaunay prescription.