“…Then, there exists a local semi‐strong solution ( ρ , u , w ) of – in Ω×(0, T ). The functions u , w , ρ , and p , defined on (0, T ∗ ), for some T ∗ ∈(0, T ], are such that Remark (, Remark 2) If Ω is either bounded or , the regularity for the density is ρ t ∈ L ∞ (0, T ∗ ; L ∞ (Ω)) and ∇ ρ ∈ L ∞ (0, T ∗ ; L ∞ (Ω)). This fact is due to known results on the regularity of the Stokes problem in such domains (Remark ).…”