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PROGRAM SUMMARY
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**
Title of program:
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ym3dsu2.cc
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Catalogue identifier:
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ADLN
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Ref. in CPC:
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125(2000)282
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Distribution format: ** tar gzip file
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Operating system: ** UNIX
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Number of lines in distributed program, including test data, etc:
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6647
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Programming language used: ** C++
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Computer: ** PC

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Nature of physical problem:
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Coherence effects are important in the description of the formation and
evolution of the quark gluon plasma in ultra-relativistic heavy-ion
collisions. In particular the description of the initial state of the
two colliding nuclei requires the coherent evolution of colour fields
generated by random sources. In order to develop an appropriate
transport model for the early stage of high energetic nuclear collisions
it is therefore necessary to study first pure Yang-Mills field dynamics
as a coherent mean-field model for the gluon fields.

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Method of solution
**

Gluon dynamics at small x can be viewed as coherent Yang-Mills dynamics
with fast random colour sources. Therefore, it is useful to study
classical Yang-Mills dynamics in three dimensions. The computer program
presented here, allows a demonstration of the simple cases.
The soft gluon fields of two colliding nuclei are modelled as Gaussian
wave packets in the framework of Yang-Mills theory. In this simple
approach valence quarks and sea quarks are omitted. The structure of
the nuclei is neglected or smeared out by initially uniform field
distributions.
The dynamics of colour degrees of freedom is considered within the
framework of a SU(2) gauge symmetry. Soft gluon scattering and
time-delayed gluon radiation are studied with this simple mean-field
approach by an analysis of the time evolution of energy currents and
energy distributions in various dimensions and projections as well as
their Fourier spectra. The time evolution of the fields is described by
the Yang-Mills equations and carried out on a gauge lattice within the
Hamiltonian formulation of Kogut and Susskind.

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Restrictions on the complexity of the problem
**

In the present version of the code we only consider Yang-Mills fields
and their time-evolution in the SU(2) gauge symmetry. The extension
towards SU(N) gauge symmetry can be carried out in a straight forward
manner. Uniformly colour polarized wave packets of Gaussian shape are
used to describe the soft glue fields of two colliding nuclei.