This is seems to be quite hampered by only including references that are found in the arXiv. Two of my papers from grad school are surrounded by papers that have very little to do with them. My three papers that are on the arXiv are very spread out, with the distance between two of them being ~90% of the map height and the third somewhere in the middle. They are all in physics, but very focused on experiment and apparatus. I think that physics theory (vs. experiment) is over-represented on the arXiv and connections to theory papers are much more influential on the map. It would be interesting to redo this with a database like http://adsabs.harvard.edu/, which doesn't depend on author self-selection.
