  We propose a hybrid model of simplicial quantum gravity by performing at once
dynamical triangulations and Regge calculus. A motive for the hybridization is
to give a dynamical description of topology-changing processes of Euclidean
spacetime. In addition, lattice diffeomorphisms as invariance of the simplicial
geometry are generated by certain elementary moves in the model. We attempt
also a lattice-theoretic derivation of the black hole entropy using the
symmetry. Furthermore, numerical simulations of 3D pure gravity are carried
out,exhibiting a large hysteresis between two phases. We also measure geometric
properties of Euclidean `time slice' based on a geodesic distance, resulting in
a fractal structure in the strong-coupling phase. Our hybrid model not only
reproduces numerical results consistent with those of dynamical triangulations
and Regge calculus, but also opens a possibility of studying quantum black hole
physics on the lattice.
