The work about collective string-like gluon fields,
the color ropes [16] ,
published in 1985,
originates in an idea of mine how to describe
random color charges of higher SU(3) multiplets.
Dr. ** J.Knoll ** contributed to the success of this work
essentially by drawing the attention to Schwinger's
quark production model in classical electric fields
and ** H. B. Nielsen ** supported us with his
expertise in field theory.

Recently (1992 - 1995) a renewed interest in the
color rope model can be noted since those microscopic models
of relativistic heavy ion collisions which are based on
individual strings cannot comply with enhanced strange
hadron production observed in CERN SPS heavy ion
experiments. The ** Q**uark -**G**luon **S**tring **M**odel
[** L.P.Csernai, L.Bravina **] and the
**R**elativistic **Q**uantum**M**olecular **D**ynamics
[** H.Sorge **] can explain this enhancement by assuming color ropes.

The gaussian effective potential method is a variational approach which treats the ground state wave functional as a gaussian; the reminescent of oscillator ground state wave function. The parameters of this ansatz - in the field theory classical fields and gluon propagators - obey (integro differential) equations derived from minimizing the corresponding thermodynamical potential (Gibbs potential at a given temperature and baryochemical potential) [25, 29, 31, 70] .

Heavy color charges (e.g. quarks) on such a background minimize the energy of chromoelectric field spanned between them. As a result a linear + Coulomb potential energy occurs effectively at zero temperature while a combination of Yukawa and Coulomb terms at overcritical temperatures, where the gluons acquire a dynamical mass in the hot plasma but the gluon condensate vanishes [27, 35, 72] .

A system of heavy quarks can be described by using
non-relativistic interquark potentials to a good
approximation. Based on a **S**tring-**B**ag **M**odel
[23] which unifies the
phenomenological confining potential with a color spin -
color spin coupling (Ising model like) factor it is
possible to consider color non-singlet quark pairs as well.
In this case the effects of medium
quark gluon plasma
are taken into account by mirror charges, so non-singlet
color charge clusters automatically carry an energy
diverging with the system size (this is the "bag" part).

With ** W. Cassing **
we studied in this model multi-quark systems, especially
six quarks, in canonical equilibrium at a given temperature
by calculating the partition sums for randomly located
charges. The system size was inversely proportional to
the temperature. An equilibrium distance between the
quarks gathering into a singlet state can be observed at
low temperature, while above a critical value all
interquark distances are the same and scale with the
(inverse) temperature.

While for light quarks only hadrons with a minimum number
of valence quarks (2 or 3) can exist, the idea occurs that
exotic multi quark systems consisting of heavy
(charm, bottom or top) quarks may be produced in relativistic
heavy ion collisions. This possibility depends on
phenomenological parameters which may be different
in these physical processes.
Together with ** P. Lévai ** and ** J. Zimányi **
we concluded that
unfortunately the parameter window allowing such objects
to exist is rather tiny
[77,
115] .