Hi everyone,(adsbygoogle = window.adsbygoogle || []).push({});

This is a question about conformal field theory. Even though it is not directly about beyond the SM, it seems like an appropriate place to ask since it is an important tool in string theory.

I am confused by the fusion rules [itex] \phi_i ~ \phi_j = N^k_{ij} \phi_k [/itex]

(where as usual this is meant to be relating conformal families). My confusion is due to the fact that the N coefficients may in general be different from 0 or 1. What does it mean to have a coefficient larger than 1? Books mention in passing something about having several ways to fuse the families but they never explain and then stop talking about it because the entries of N are only 0 or 1 in the minimal models. Can someone shed some light on this?

thanks!

Patrick

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Fusion rules in CFT

**Physics Forums | Science Articles, Homework Help, Discussion**