If the matter is a mixture of two or more non-interacting fluids each with such an equation of state, then ρ ρ ˙ ˙ f = − − 3 H ( ρ ρ f + p f c 2 ) holds separately for each such fluid f. In each case, ρ ρ ˙ ˙ f = − − 3 H ( ρ ρ f + w f ρ ρ f ) from which we get ρ ρ f ∝ ∝ a − − 3 ( 1 + w f ) .