TITLE: Should one post a paper on the arXiv if it is not intended to be published?
QUESTION [37 upvotes]: A brief description: I have written a paper which contains a new result which I believe is somewhat important but not vital to the field.  It is a generalization of an existing proof to get significant new information, in a framework that did not exist at the time of the original paper (not by me).  I do not believe the result can be recovered from the original result, only from the proof, which is lengthy.
The paper as it stands is self-contained but a significant portion is a reproduction of the original paper (recovering additional information from various lemmas).  Some lemmas are new but many are old.  A copy of it which does not reproduce original work is only about 5 pages long but is very difficult to read.
It is my adviser's opinion (and I agree) that neither form of the paper is suitable for publication, for different reasons.  We both believe the result on its own is significant enough, though.  So, the question: would posting the long form on the arXiv as is be appropriate?
To head off the obvious question: yes, the author of the original paper is prominently pointed out in the abstract and the introduction, where it is pointed out that we follow the original proof closely in most cases.

REPLY [2 votes]: Given that arxiv is a pre-print publication site and many of the hosted papers are not published elsewhere, yes i would say you should post it there.
Note that arxiv (and various similar sites like vixra) is good for other functions as well. For example we know the journals are sometimes heavily refereed and not everything published might be the best (for example if by an otherwise important author) and/or not everything important is published (for example by a relatively unknown author or sth very contrived)
Apart from that, personaly i think that sites like arxiv enable research and technology to go further by allowing partial or otherwise un-published results (see above) be published even in this format
i make heavy use of arxiv and of course i am aware that sometimes invalid results get publishd there.
Furthermore this would give you something like a copyright license (e.g "i published it on arxiv on that date") or to be more precise since i am not fan of copyright. It would give you the chronological advantage if you like