From quantum foam to graviton condensation: the Zel'dovich route

Based on a previous ansatz by Zel'dovich for the gravitational energy of virtualparticle-antiparticle pairs, supplemented with the Holographic Principle, we estimate the vacuumenergy in a fairly reasonable agreement with the experimental values of the Cosmological Constant.We further highlight a connection between Wheeler's quantum foam and graviton condensation,as contemplated in the quantum N-portrait paradigm, and show that such connection also leads toa satisfactory prediction of the value of the cosmological constant. The above results suggest thatthe "unnaturally" small value of the cosmological constant may find a quite "natural" explanationonce the nonlocal perspective of the large N-portrait gravitational condensation is endorsed.