The cosmological constant may be interpreted as a form of negative pressure, which Einstein originally used to counter this self-attraction. He wanted to prevent the universe either expanding or collapsing to yield a static universe, the CC balanced the gravitational forces on a large scale within the universe.
So the negative pressure which is the CC will yield a static universe?
When observations of distant Type Ia super novae were interpreted to indicate that the unverse was actually accelerating, not decelerating as previously expected, then a negative pressure was invoked to deliver this.
So the negative pressure which is the CC will yield an accelerating expanding universe?
How can an equation containing one particular (in this case negative pressure in both cases) constant yield two solutions that contradict each other? That is a static universe and an acclerating expanding universe.