Gauge Invariance from a Graphical Self-Consistency Criterion
  We propose that quantum physics is the continuous approximation of a more fundamental, discrete graph theory (theory X). Accordingly, the Euclidean transition amplitude Z provides a partition function for geometries over the graph, which is characterized topologically by the difference matrix and source vector of the discrete graphical action. The difference matrix and source vector of theory X are related via a graphical self-consistency criterion (SCC) based on the boundary of a boundary principle on a graph. In this approach, the SCC ensures the source vector is divergence-free and resides in the row space of the difference matrix. Accordingly, the difference matrix will necessarily have a nontrivial eigenvector with eigenvalue zero, so the graphical SCC is the origin of gauge invariance. Factors of infinity associated with gauge groups of infinite volume are excluded in our approach, since Z is restricted to the row space of the difference matrix and source vector. Using this formalism, we obtain the two-source Euclidean transition amplitude over a (1+1)- dimensional graph with N vertices fundamental to the scalar Gaussian theory. 
W.M. Stuckey, Timothy McDevitt and Michael Silberstein
quant-ph