title: 3nj Morphogenesis and semiclassical disentangling.
abstract: Recoupling coefficients (3nj symbols) are unitary transformations between binary coupled eigenstates of N = (n + 1) mutually commuting SU(2) angular momentum operators. They have been used in a variety of applications in spectroscopy, quantum chemistry and nuclear physics and quite recently also in quantum gravity and quantum computing. These coefficients, naturally associated to cubic Yutsis graphs, share a number of intriguing combinatorial, algebraic, and analytical features that make them fascinating objects to be studied on their own. In this paper we develop a bottom-up, systematic procedure for the generation of 3nj from 3(n - 1)j diagrams by resorting to diagrammatical and algebraic methods. We provide also a novel approach to the problem of classifying various regimes of semiclassical expansions of 3nj coefficients (asymptotic disentangling of 3nj diagrams) for n > or = 3 by means of combinatorial, analytical and numerical tools.
authors.affiliation: Department of Chemistry, University of California, Santa Cruz, California 95064, USA.
authors.forename: Roger W
authors.initials: RW
authors.lastname: Anderson
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Aquilanti
authors.forename: Annalisa
authors.initials: A
authors.lastname: Marzuoli