The transfer matrix in four-dimensional CDT
  The Causal Dynamical Triangulation model of quantum gravity (CDT) 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 labeled 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. 
Jan Ambjorn, Jakub Gizbert-Studnicki, Andrzej G\"orlich, Jerzy   Jurkiewicz
hep-th gr-qc hep-lat