| Summary: | We study the four-quark interaction as a first step in understanding the
QCD origin of the nuclear force in nature. We simulate QCD on a 20 x 20 x 20 x 32
space-time lattice with the simplifying quenched and static approximations, and
with the SU(2) gauge group. Recent four-quark simulations reveal interesting tetrahedral
geometry and planar four-quark flux distributions that cannot be explained
by existing models. We simulate the flux distribution for the still-unexplored next
higher level of geometrical complexity, namely four quarks on the corners of a tetrahedron.
In order to complete the simulation within the allotted computing time,
we have improved the approach used to simulate the flux distribution. Compared
to previous approaches, the new approach nearly eliminates the bottleneck of the
computing time, provides more than a 100-time speedup in our project, and also
provides a better strategy for improving signal-noise ratio and suppressing signal
distortion from the lattice structure. As the result of this improved approach, we
have observed the long diagonal flux tube structure, repeated the Helsinki group's
1998 results for the flux distribution of a square geometry, and, for the first time,
simulated the flux distribution of a tetrahedron geometry. In this thesis, we also
explore some fundamental questions of lattice QCD related to computability theory
and complexity theory. === Graduation date: 2001
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