On the total mass of closed universes with a positive cosmological constant

The recently suggested notion of total mass density for closed universes is extended to closed universes with a positive cosmological constant. Assuming that the matter fields satisfy the dominant energy condition, it is shown that the cosmological constant provides a sharp lower bound for the total mass density, and that the total mass density takes this as its minimum value if and only if the spacetime is locally isometric with the de Sitter spacetime. This notion of total mass density is extensible to non-compact 3-spaces of homogeneity of Bianchi class A cosmological spacetimes.