[cdtwigg]

Okay, so these papers are phrased a little confusingly, but what they're really doing is solving a specific but very useful type of linear equation Ax = b where A is a diagonally-dominant matrix (entries on the diagonal are larger than the sum of the off-diagonal entries). It happens that graphs are equivalent to matrices, so it's a neat area that straddles applied math and computer science. For a survey paper on recent developments in the field: http://www.cs.cmu.edu/~jkoutis/papers/CACM-KMP.pdf