# What means “extended concepts of symmetry”?

Where could one find a short description oft: "two mathematical extensions of the symmetry - to moduli spaces of sheaves and to derived categories", found here? Happen there interesting things like with the moduli spaces of pointed curves etc.?

-
Presumably this is an attempt to work around the fact that the sporadic group $M_{24}$ appears to act on some structure underlying the elliptic genera of K3 surfaces (see Eguchi-Ooguri-Tachikawa), but does not actually act on the surfaces themselves. Rather than explicitly constructing an object with $M_{24}$ symmetry, one may cheat and try to redefine the word "symmetry" (although I don't know a canonical choice of new definition). –  S. Carnahan Dec 13 '11 at 18:29
Thanks Scott, but for me that passage sounds as if it wold refer to some new general principle, hmm... –  Thomas Riepe Dec 14 '11 at 8:41