  We study the impact of large lepton flavour asymmetries on the cosmic QCD
transition. Scenarios of unequal lepton flavour asymmetries are observationally
almost unconstrained and therefore open up a whole new parameter space for the
cosmic QCD transition. We find that for large asymmetries the formation of a
Bose-Einstein condensate of pions can occur and identify the corresponding
parameter space. In the vicinity of the QCD transition scale, we express the
pressure in terms of a Taylor expansion with respect to the complete set of
chemical potentials. The Taylor coefficients rely on input from lattice QCD
calculations from the literature. The domain of applicability of this method is
discussed.
