Efimov trimers in a harmonic potential

We study the Efimov effect in a harmonic oscillator in the hyperspherical formulation, and show how a reduced model allows for a description that is a generalization of the Efimov effect in free space and leads to results that are easily interpreted. Three-particle states that resemble Efimov trimers for large scattering length, become more similar to independent particles in a harmonic trap when adiabatically decreasing the scattering length. In the transition region, Efimov physics may be observed, while the increased size of the bound states reduces decay into more deeply bound states. The model also allows for the study of non-universal Efimov trimers by including the effective range scattering parameter. While we find that in a certain regime the effective range parameter can take over the role of the three-body parameter, interestingly, we obtain a numerical relationship between these two parameters different from what was found in other models.