Gravitational Aether and the thermodynamic solution to the cosmological   constant problem
  Cosmological constant problem (in its various versions) is arguably the deepest gap in our understanding of theoretical physics, the solution to which may very likely require revisiting the Einstein theory of gravity. In this letter, I argue that the simplest consistent way to decouple gravity from the vacuum energy (and hence solve the problem) is through the introduction of an incompressible gravitational aether fluid. The theory then predicts that gravitational constant for radiation is 33% larger than that of non-relativistic matter, which is preferred by most cosmological observations (with the exception of light element abundances), but is not probed by current precision tests of gravity. I also show that slow-roll inflation can happen in this theory, with only minor modifications. Finally, interpreting gravitational aether as a thermodynamic description of gravity, I propose a finite-temperature correction to the equation of state of gravity, which would explain the present-day acceleration of the cosmic expansion as a consequence of the formation of stellar mass black holes. 
Niayesh Afshordi (Perimeter Institute)