  The Causal Dynamical Triangulation model of quantum gravity (CDT) is a
proposition to evaluate the path integral over space-time geometries using a
lattice regularization with a discrete proper time and geometries realized as
simplicial manifolds. The model admits a Wick rotation to imaginary time for
each space-time configuration. Using computer simulations we determined the
phase structure of the model and discovered that it predicts a de Sitter phase
with a four-dimensional spherical semi-classical background geometry. The model
has a transfer matrix, relating spatial geometries at adjacent (discrete
lattice) times. The transfer matrix uniquely determines the theory. We show
that the measurements of the scale factor of the (CDT) universe are well
described by an effective transfer matrix where the matrix elements are
labelled only by the scale factor. Using computer simulations we determine the
effective transfer matrix elements and show how they relate to an effective
minisuperspace action at all scales.
