Conformal bootstrap

Summary

The conformal bootstrap is a method to determine or constrain conformal field theories from consistency conditions alone, without a Lagrangian. It uses the operator product expansion to write a four-point function in two different ways and requires that the two agree, together with unitarity. The idea goes back to the early 1970s. Since 2008 numerical versions have produced rigorous bounds on scaling dimensions and precise critical exponents, for example for the three-dimensional Ising model.