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Manuscript Title: Rapid evaluation of four-body cluster contributions.
Authors: G.P. Mueller
Program title: FOURBODY
Catalogue identifier: ABIA_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 2(1971)214
Programming language: Fortran.
Computer: CDC 3800.
Operating system: SCOPE.
RAM: 4K words
Word size: 48
Keywords: Nuclear physics, Cluster expansion, Numerical integration, Four-body contributions, Haselgrove, Alpha matter, Monte-carlo, Equidistributed Sequence, Cluster model.
Classification: 17.21.

Nature of problem:
Within the framework of the cluster expansion formalism we present a method for rapidly evaluating the four-body contributions to the ground state energy of an extended system of bosons, specifically, alpha matter. Since the numerical results for alpha matter have been published elsewhere, we present here a fictitious example for which the exact results are obtainable.

Solution method:
These calculations involve the numerical integration of six-dimensional integrals, which we evaluate using a method due to Haselgrove. For the same accuracy, this method seems to require less running time and oi easier to program than more conventional methods.

The program is restricted to the evaluation of six-dimensional integrals, but can easily be modified to evaluate an integral of almost any dimension.

Running time:
Approximatley 15 s are needed on the CDC 3800 for results that are accurate to 5% for the example given here. For a more realistic problem, perhaps twice that much running time would be needed.