Λ/8, or

The cosmological constant Λ is derived from the radius of the observable universe. The corresponding value of vacuum energy density is equal to the value derived from zero-point energy on the boundary, at the scale of the Bohr Radius, of a six-dimensional AdS spacetime. The two length scales are related. The cosmological constant Λ has the dimensions [L]-2 and defines a length scale . Drawing on the Holographic Principle [1], which declares that the physics of a space is encoded on the boundary of that space, and since Λ is an intrinsic property of the vacuum, we will associate with the radius of the observable universe, =14,300 Mpc [2]