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[Licence| Download | New Version Template] adrm_v2_0.tar.gz(531 Kbytes)
Manuscript Title: Gyutsis: heuristic based calculation of general recoupling coefficients.
Authors: D. Van Dyck, V. Fack
Program title: GYutsis: VAN DYCK, FACK
Catalogue identifier: ADRM_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 154(2003)219
Programming language: Java.
Computer: Any with Sun's Java 4.1.
Operating system: Windows, Linux, Unix.
Keywords: Angular momentum, General recoupling coef, Yutsis graph, Reduction rules, Cyclic structure, Heuristic, Computational Methods.
Classification: 4.1.

Nature of problem:
A general recoupling coefficient for an arbitrary number of (integer or half-integer) angular momenta can be expressed as a formula consisting of products of 6-j coefficients summed over a certain number of variables . Such a formula can be generated using the program GYutsis (with a grap hical user front end ) or CycleCostAlgorithm (with a text-mode user fron t end).

Solution method:
Using the graphical techniques of Yutsis, Levinson and Vanagas (1962) a summation formula for a general coupling coefficient is obtained by representing the coefficient as a Yutsis graph and by performing a selection of reduction rules valid for such graphs. Each reduction rule contributes to the final summation formula by a numerical factor or by an additional summation variable. Whereas an optimal summation formula (i.e. with a minimum number of summation variables) is hard to obtain, we present here some new heuristic approaches for selecting an edge from a k-cycle in order to transform it into a (k-1)-cycle (k>3) in such a way that a "good" summation formula is obtained.

Running time:
From instantaneously for the typical problems to 30 s for the heaviest problems on a Pentium II-350 Linux-system with a 256MB RAM.