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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.

Restrictions:
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.