Quark matter
in bulk is often described by an equation of state of interacting quarks to first
order in 
[10,11]
Here 
and 
denote the (current) mass and the chemical potential,
respectively, of the quark flavour i=u,d,s.
For the total potential the vacuum excitation energy BV
has to be added. It corresponds to the energy difference between the
`false', perturbative vacuum inside the `bag' and the true vacuum on the
outside
From this expression (10)
the energy per baryon in the groundstate can be
readily obtained. The derivative of E/A with respect to the baryon density
is zero if the system is at zero pressure. In Fig. 18 the resulting groundstates are shown
for 
and different bag-parameters a function of the strangeness
fraction 
. The energy per baryon of the corresponding hyperonic matter
(taken from the RMF model 1) is also drawn. The tangent construction
shown proves that for a given strangeness fraction the separation of a normal and a highly strange subsystem
might be energetically favorable as compared to the mixture. Therefore it is energetically advantageous to accumulate
the strangeness in the quark phase!
Figure 
: The tangent construction at T=0.
For a given strangeness fraction 
the specific energy 
is lowest for a two-phase mixture of quark and
hadronic matter. Drawn are the masses of non-interacting quark matter for
different bag parameters and 
MeV (QGP) and those of infinite
hadronic matter in the RMFT model 1 (full line) and model 2 (dashed) [29].
