PerspectivePhysics

Universal Few-Body Binding

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Science  18 Dec 2009:
Vol. 326, Issue 5960, pp. 1640-1641
DOI: 10.1126/science.1184235

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Summary

Predicting the binding rules of quantum particles is a formidable task. Even for as few as three particles, one would need to know precisely all the details of the mutual interactions among them. Notable exceptions have been predicted to arise if the interaction between the particles is very large, a condition where universal binding laws are expected to appear (1, 2). Because no available physical system composed of atoms, nuclei, or even elementary particles was suitable to observe the phenomenon, these ideas have been mainly confined to theory. On page 1683 of this issue, Pollack et al. (3) present evidence for the presence of universal scaling laws simultaneously occurring for three- and four-body bound states in an ultracold atomic system. The observation confirms both old and new theoretical predictions, thus providing a fuller understanding of universal binding.