%0 Journal Article
%T Universal behaviour of four-boson systems from a functional renormalisation group
%A Benjamin Jaramillo Avila
%A Michael C. Birse
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevA.88.043613
%X We apply a functional renormalisation group to systems of four bosonic atoms close to the unitary limit. We work with a local effective action that includes a dynamical trimer field and we use this field to eliminate structures that do not correspond to the Faddeev-Yakubovsky equations. In the physical limit, we find three four-body bound states below the shallowest three-body state. The values of the scattering lengths at which two of these states become bound are in good agreement with exact solutions of the four-body equations and experimental observations. The third state is extremely shallow. During the evolution we find an infinite number of four-body states based on each three-body state which follow a double-exponential pattern in the running scale. None of the four-body states shows any evidence of dependence on a four-body parameter.
%U http://arxiv.org/abs/1304.5454v3