Viscous gravitational aether and the cosmological constant problem

Abstract

Recently a notion of gravitational aether is advocated to solve thecosmological constant problem. Through the modification of thesource of gravity one finds that the effective Newton's constant issource dependent so as to provide a simple but consistent way todecouple gravity from the vacuum energy. However, in the originalpaper the ratio of the effective Newton's constants for pressurelessdust and radiation has an upper bound which is 0.75. In this paperwe propose a scheme to loose this bound by introducing a bulkviscosity for the gravitational aether, and expect this improvementwill provide more space for matching predictions from thistheoretical programm with observational constraints.