Q: Why are there so many more physics papers than other, non-physics categories?
A: The categories astro-ph, cond-mat and math each account for about 13% of the number of papers on the arXiv (i.e. 39% combined). Whilst hep-th and hep-ph account for only 5.8% and 7.1% respectively. These latter categories are more prominent on the map simply because they have more citations (acconding to our citation processor) and hence more area on the map.

Q: Why do some papers appear in a strange location?
A: A paper’s location is determined by its references. If our bibliography parser does not find the references (either because they don’t exist in the arXiv, or because we fail to find the link) then the paper might be placed in a non-ideal location. If we do not find any references for a given paper, then we use keywords from the title and abstract to place it close to other papers that also have those keywords.

Q: Why do cs and math categories have mostly tiny papers?
A: Because we currently do not have enough refererence information for these papers, and hence they are drawn with the minimum radius.