I am doing a project on the inverse Galois problem, and am seeking to show that the monster group is realisable over the rationals. I have heard that the monster group has found uses in theoretical physics, and was wondering what those uses might be. Also, is there any practical significance to theoretical physics in the result I am aiming to prove?

3$\begingroup$ Take a look at mathoverflow.net/questions/13851/… for information on realizing the Monster group as a Galois group over Q. No mention there of applications to physics, so this is not a direct answer to the question. $\endgroup$ – KConrad Mar 20 '11 at 19:52

4$\begingroup$ There is a book called "Moonshine Beyond the Monster: the bridge connecting Algebra, Modular Forms and Physics" which was written by Terry Gannon. I think it's probably a good idea for you to take a look at it ;). $\endgroup$ – Max Muller Mar 21 '11 at 8:11
There are presently no applications of the monster group in physics, though there is a lot of misleading speculation about this. However in the other direction there are some applications of ideas from physics to the monster group. In particular the noghost theorem in string theory is used to construct the monster Lie algebra acted on by the monster group.
The ideas from physics seem to have no direct connection with the problem of realizing the monster as a Galois group over the rationals. This was solved by Thompson, who showed by charactertable calculations that the monster satisfies a sufficient condition ("rigidity") for it to be a Galois group.

1$\begingroup$ The wikipedea link for the "no ghost" theorem is en.wikipedia.org/wiki/Goddard%E2%80%93Thorn_theorem $\endgroup$ – Gil Kalai Mar 21 '11 at 19:30

3$\begingroup$ I know very little about the subject; But you can check this lecture : youtube.com/watch?v=F5BsXalOdDU by Ed Witten where he links the Monster group to quantizing gravity in 2+1 dimensions. In particular, the lecture contains a very interesting derivation of black hole entropy in 2+1 as $log(196883) = 12.19$.. , where the classical entropy is $4*\pi = 12.57$ which is off by a few percent. What do you think of that professor Borcherds? $\endgroup$ – Mohamed Alaa El Behairy Jun 9 '11 at 6:28