What's the current state of Yang–Mills mass gap question, is there any place that does this problem? Especially I want to know if there is any progress (out of that mentioned in the introduction article by Witten and Jaffe). Is it too hard for a mathematician? Thanks!

$\begingroup$ marcofrasca.wordpress.com/2010/09/03/… $\endgroup$– user11219Dec 1 '10 at 4:59

$\begingroup$ Added tag: openproblem $\endgroup$– Daniel MoskovichDec 1 '10 at 11:07

$\begingroup$ marcofrasca.wordpress.com/2010/12/01/… $\endgroup$– user11226Dec 1 '10 at 11:46
There's some guidelines about open problems in the FAQ that you might want to read, but there was a good article by Faddeev last November that you should know about:
There is a rather strange situation here because a russian mathematician, Alexander Dynin, is claiming to have solved it. Please, refer to this question of mine or this paper published in a reputable journal. Till now I have not seen any reaction from the community but I think that an analysis of the work of this author is overdue. Indeed, he has worked on this since 2009 as I can see from arxiv.
For the 3D version of the proble, see
[1] Dimitra Karabali and V. P. Nair, Int. J. Mod. Phys. A 12, 1161 (1997) http://arxiv.org/abs/hepth/9610002
See eqn (20), (21) and the following paragraph.

1$\begingroup$ While it provides some explanations, the problem treated there is in 3 dimensions only, while the Clay Millennium problem asks for a solution in 4 dimensions, where extra difficulties show up. $\endgroup$ Apr 4 '15 at 16:24

$\begingroup$ I forgot to mention 3D. Thanks for the correction. $\endgroup$– TY1May 29 '15 at 21:55