Abstract:
A Desitter universe accepts only a constant vacuum energy density otherwise in an expanding universe decaying vacuum energy density was allowed. Vacuum energy density was supposed to decay into matter. A decaying vacuum energy density was found to be related to the gravitational field also it depends on the kind of the universe whether open, closed or flat. A decaying vacuum energy depending on the inverse of the square of the scale factor is related to the weak gravitational field while a power series function in the inverse of the square of the scale factor was allowed in the strong gravitational field which means that the functional form of the vacuum energy density is highly affected by the strength of the gravitational field.
