Amazing. This got me thinking about citation counts. The most cited paper in Computer Science of all time is Vapnik's Statistical Learning Theory (1998) with about 10k citations. The most cited paper of any kind of all time is Protein measurement with the folin phenol reagent by Lowry et al. (1951) with > 300k citations. There's a big time gap here, but not big enough to make up for a > 290k difference in citations. I always thought that CS was one of the more prolific paper writing communities, clearly not the case.
PS. I'm not sure which paper in the arXiv has the greatest number of citations. I don't think either of these papers are there.
That line of reasoning isn't convincing to me (though I have no data to confirm or deny it); CS could still be a more prolific paper writing community, just that papers compete more for citations. In CS if I want to cite something, I have my choice of 10 papers from the same era from roughly the same group of people saying roughly the same thing (some might prefer to cite earlier papers, as the "original", others might prefer later papers as the ideas are more clarified). In other fields, there might be one "standard" paper to cite for a era/topic/group.
Couldn't you say the same about other fields? Although I understand where you are coming from. If I wanted to make a more accurate comparison it'd only be fair to examine the distributions of different fields as well as their top performers, but I still think that is too huge a gap to make up for anything besides some heavily skewed distributions.
In CS it's customary to stop citing papers at some point. E.g., lots of papers are published about Turing machines without citing Turing.
Also, absolute limitations on page count is really common in CS, and the page counts tend to be pretty low. In other areas, journals might allow for more citations or citations might not count toward page count.
> Have there been any significant CS papers published in the last ~5 years that aren't on Arxiv?
Even if not, there might be insignificant CS papers not indexed by Arxiv which cite significant papers which are indexed ;) This makes the citation counts comparatively lower if most insignificant physics papers are in Arxiv.
That said, it doesn't surprise me much that worldwide there are still more people working in physics, biology or mathematics than in CS.
It is true that CS is more conference-oriented, however most top conferences require that a paper be submitted, reviewed, and (if accepted) published in the conference proceedings before you can present your work there. This does vary by discipline though: algs/theory is more traditional journal oriented, I believe.
My initial estimation of 10k was from a CiteSeer list that I didn't realize was limited to only documents in the CiteSeer database: http://citeseer.ist.psu.edu/stats/articles
PS. I'm not sure which paper in the arXiv has the greatest number of citations. I don't think either of these papers are there.