Two-Body and Three-Body Contacts for Three Bosons in the Unitary Regime: Analytic Expressions and Limiting Forms

Abstract

The two- and three-body contacts are central to a set of univeral relations between microscopic few-body physics within an ultracold Bose gas and its thermodynamical properties. They may also be defined in trapped few-particle systems, which is the subject of this work. In this work, we focus on the unitary three-body problem in a trap, where interactions are as strong as allowed by quantum mechanics. We derive analytic results for the two- and three-body contacts in this regime and compare them with existing limiting expressions and previous numerical studies.