Quantum exclusion of positive cosmological constant?

We show that a positive cosmological constant is incompatible with the quantum-corpuscular resolution of de Sitter metric in form of a coherent state. The reason is very general and is due to the quantum self-destruction of the coherent state as a result of the scattering of constituent graviton quanta. This process creates an irreversible quantum clock, which precludes eternal de Sitter. It also eliminates the possibility of Boltzmann brains and Poincare recurrences. This effect is expected to be part of any microscopic theory that takes into account the quantum corpuscular structure of the cosmological background. This observation puts the cosmological constant problem in a very different light, promoting it, from a naturalness problem, into a question of quantum consistency. We are learning that quantum gravity cannot tolerate exceedingly-classical sources. "Cosmological constant was originally introduced by Einstein. In classical general relativity this source creates a metric of constant space-time curvature, the so-called de Sitter space. In the context of modern quantum field theory this possibility causes a tremendous puzzle, that goes under the name of the Cosmological Constant Problem: Why is the observational bound on the cosmological term by 120 orders of magnitude smaller then its naturally-expected value set by the Planck scale? In the present paper, a very different road is suggested, by fundamentally changing the nature of the question. Instead of a naturalness problem the cosmological constant has to be viewed as a question of quantum consistency; can quantum gravity tolerate a truly constant classical source? In the present paper we provide evidence that de Sitter space cannot be eternal in quantum theory.