Transfer from four-body to effective three-body chaotic phase space

Characterize the transfer of the probability distribution from the full four-body chaotic phase space to an effective reduced three-body chaotic phase space in the hard-binary regime, in order to extend density-of-states methods to systems containing a sufficiently hard binary.

Background

The paper develops a density-of-states description of the binary-binary (2+2) outcome of the chaotic, non-hierarchical four-body problem and compares its predictions with FEWBODY scattering simulations. The comparison reveals a discrepancy in the hard-binary regime, where one binary is much more tightly bound than the overall four-body energy scale and may dynamically behave as an effective single body.

The authors hypothesize that, in this regime, the system no longer explores the full four-body chaotic phase space, but instead occupies an effective reduced three-body chaotic phase space. The mechanism governing the transition between these phase spaces is unresolved and is identified as a natural extension of density-of-states methods.