General relativity derives that positive vacuum energy density will elicite an attractive gravitational "force" which will interact with massive objects. Vacuum energy density is already comparitively higher in the region of space immediately surrounding massive clusters, since real and virtual pair production is more likely to occur where there are concentrated levels of matter and radiation. The gravitational effect serves to maintain a minimal field of posititive vacuum energy density immediately surrounding massive clusters, and this, in turn, causes more vacuum energy to be "attracted" to this region of space. If General Relativity is correct, then vacuum energy cannot be evenly distributed throughout the universe and the vacuum of quantum field theory is flawed, as there is a region of gravitationally "attractive" positive vacuum energy density which surrounds massive clusters. The causal mechanism for gravity then falls directly out of the knowledge that concentrated levels of mass energy are actually interacting with concentrated levels of vacuum energy, so locally, there is enough of the relevant energy to cut a viable attractive field. GR also supports that the creation of a particle pair from the vacuum causes the surrounding region to tend to expand proportionally, due to the increased gravitational effect, as the boundary contracts due to increasing tension, while negative pressure increases in proportion to the "hole". Concentrated regions of positive vacuum energy density enable the vacuum to expand without running away, and without any work being done, since mass energy is immediately balanced with vacuum energy via the increased gravitational effect. So the universe expands naturally, without running away, and without any work being done, because concentrated levels of mass-energy interact with the vacuum to produce relatively higher positive regions of vacuum energy density. The generated vacuum energy and the associtated negative pressure componet are immediately counterbalance with mass energy via the increased positive gravitational effect that gets induced by regions of positive vacuum pressure, and/or relatively higher energy density levels.
