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 because 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.
