However, there’s still some difference between the light elementary particle species – and the numerous heavy elementary particle species such as the black hole. The latter may still be described as some kind of “composites” of the former ones. However, string/M-theory has made the notion of compositeness more subtle. Compositeness has been de facto replaced by the UV/IR-mixing.

What is that? It’s a rule that in a theory that is as powerful as string theory and/or quantum gravity, the spectrum of elementary particles is far from arbitrary. In fact, the statistical details of the high-mass spectrum (and the properties of high-mass particles) is fully encoded in the properties of the low-mass excitations and vice versa!

— Unification as a source of certainty

— Lubos Motl

2013.04.10 Wednesday ACHK