Tuning the mass density of a closed dust filled universe can give us a long lived closed universe? General Relativity can tell us how that mass density changes with time? Instead of dust let us have a real field defined at each point of spacetime. Let us assume the field is such that in some frame the field has no momentum and only energy? Assume the energy density of the field changes with time just as the energy density of a dust filled universe. How might the amplitude (and frequency) of this field change with time so that this might happen? Thanks for any help.