Viscous gravitational aether and the cosmological constant problem

Recently a notion of gravitational aether is advocated to solve the cosmological constant problem.Through the modification of the source of gravity one finds that the effective Newton's constant is source dependent so as to provide a simple but consistent way to decouple gravity from the vacuum energy.However,in the original paper the ratio of the effective Newton's constants for pressureless dust and radiation has an upper bound which is 0.75.In this paper we propose a scheme to loose this bound by introducing a bulk viscosity for the gravitational aether,and expect this improvement will provide more space for matching predictions from this theoretical programm with observational constraints.