The Atoms Of Space, Gravity and the Cosmological Constant
  I describe an approach which connects classical gravity with the quantum microstructure of spacetime. The field equations arise from maximizing the density of states of matter plus geometry. The former is identified using the thermodynamics of null surfaces while the latter arises due to the existence of a zero-point length in the spacetime. The resulting field equations remain invariant when a constant is added to the matter Lagrangian, which is a symmetry of the matter sector. Therefore, the cosmological constant arises as an integration constant. A non-zero value $(\Lambda)$ of the cosmological constant renders the amount of cosmic information $(I_c)$ accessible to an eternal observer finite and hence is directly related to it. This relation allows us to determine the numerical value of $(\Lambda)$ from the quantum structure of spacetime. 
T. Padmanabhan
gr-qc astro-ph.CO hep-th