  Lattice QCD studies of the thermodynamics of the hot quark-gluon plasma (QGP)
demonstrate the importance of accounting for the interactions of quarks and
gluons, if one wants to investigate the phase structure of strongly interacting
matter. Motivated by this observation and using state-of-the-art results from
perturbative QCD, we construct a simple effective equation of state for cold
quark matter that consistently incorporates the effects of interactions and
furthermore includes a built-in estimate of the inherent systematic
uncertainties. This goes beyond the MIT bag model description in a crucial way,
yet leads to an equation of state that is equally straightforward to use.
