In 1971, Ken Wilson pointed out that simple high-energy behavior in a quantum field theory could arise from renormalization group (RG) flow to a limit cycle as an alternative to a fixed point. In 1969, Vitaly Efimov showed that nonrelativistic bosons with a strong resonant 2-body interaction form a sequence of shallow 3-body bound states whose binding energies differ by multiplicative factors of 515 in the strong-coupling limit. A connection between these two theoretical developments has recently emerged. A simple consequence is that QCD for the physical values of the quark masses is close to the critical RG trajectory associated with an infrared limit cycle in the 3-nucleon sector.
