ArXiv

arXiv (pronounced "archive", as if the "X" were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and biology which can be accessed via the Internet. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. As of October 2006, arXiv.org contains over 390,000 e-prints, with roughly four thousand new e-prints added every month.

History
The arXiv was originally developed by Paul Ginsparg and started in 1991 as an archive for preprints in physics and later expanded to include mathematics, computer science, nonlinear science and, most recently, quantitative biology. It soon became obvious that there was a demand for long term preservation of preprints. The term e-print was adopted to describe the articles. Ginsparg was awarded a MacArthur Fellowship in 2002 for his establishment of arXiv.

It was originally hosted at the Los Alamos National Laboratory (at xxx.lanl.gov, hence its former name, the LANL preprint archive) and is now hosted and operated by Cornell University, with mirrors around the world. It changed its name and address to arXiv.org in 1999 for greater flexibility. It has also been mistakenly claimed that the origin of the original hostname "xxx" was that it was one better than "www" in every way, but xxx.lanl.gov predated the World Wide Web. Also, it is sometimes claimed that some censorware programs were preventing some users from accessing it at its previous address, xxx.lanl.gov, under the impression that the XXX in its name implied that it was a pornographic site; however, legislation such as CIPA was not passed until later, and there is no evidence that users were significantly hampered by such programs.

Its existence was one of the precipitating factors that led to the current revolution in scientific publishing, known as the open access movement, with the possibility of the eventual disappearance of traditional scientific journals. Professional mathematicians and scientists regularly upload their papers to arXiv.org for worldwide access and sometimes for reviews before they are published in peer reviewed journals.

Peer-review
Although the arXiv is not peer-reviewed, an "endorsement" system was introduced in January 2004 as part of an effort to ensure content that is relevant and of interest to current research in the specified disciplines. The new system has attracted its own share of criticism for allegedly restricting inquiry. Under the system, an author must first get endorsed. Endorsement comes from either another arXiv author who is an endorser or is automatic, depending on various evolving criteria. Endorsers are not asked to review the paper for errors, but to check if the paper is appropriate for the intended subject area.

The lack of peer-review, while a concern to some, is not considered a hindrance to those who use the arXiv. Many authors exercise care in what they post. A majority of the e-prints are submitted to journals for publication, but some work, including even very influential papers, remains purely as e-prints and is never published in a peer-reviewed journal. A well-known example of the latter is a potential proof of Thurston's geometrization conjecture, including the Poincaré conjecture as a particular case, uploaded by Grigori Perelman in November 2002. Perelman appears content to forgo the traditional peer-reviewed journal process, stating "If anybody is interested in my way of solving the problem, it's all there [on the arXiv] - let them go and read about it."

While the arXiv does contain some dubious e-prints, such as those claiming to refute famous theorems or proving famous conjectures such as Fermat's last theorem using only high school mathematics, they are "surprisingly rare" (see Jackson 2002 in references). The arXiv generally re-classifies these works, e.g. in "General mathematics", rather than deleting them. 

A few scientists, for example, Nobel laureate Brian Josephson, complain that their papers are not accepted or are forcibly recategorised by the administrators of the arXiv due to the controversial nature of their work, amounting to intellectual censorship.

Access
The standard access route is through the arXiv.org website or one of several mirrors. Several other interfaces and access routes have also been created by other un-associated organisations. These include the University of California, Davis's front, a web portal that offers additional search functions and a more self-explanatory interface for the mathematics portion of arXiv.org, and is referred to by some mathematicians as (the) Front. A similar function is offered by eprintweb.org, launched in September 2006 by the Insitute of Physics. Google Scholar and Windows Live Academic can also be used to search for items in arXiv. Finally, researchers can select sub-fields and receive daily emailings of all submissions in them.