My question concerns applications of monstrous moonshine, which is the connection between the $j$-function and the monster group. Recently, physicists have applied it to string theory and, ultimately, to a possible form of 3D quantum gravity, as seen in the article below:
However, my question is what are other applications of monstrous moonshine to physics outside string theory? Are there possible connections to conformal field theories in condensed matter physics? If not to condensed matter, what are some other possible physical applications?