paper

On the possible running of the cosmological "constant"

arXiv:0910.4925 · doi:10.1016/j.physletb.2009.10.073

Abstract

Despite the many outstanding cosmological observations leading to a strong evidence for a nonvanishing cosmological constant (CC) term in the gravitational field equations, the theoretical status of this quantity seems to be lagging well behind the observational successes. It thus seems timely to revisit some fundamental aspects of the CC term in Quantum Field Theory (QFT). We emphasize that, in curved space-time, nothing a priori prevents this term from potentially having a mild running behavior associated to quantum effects. Remarkably, this could be the very origin of the dynamical nature of the Dark Energy, in contrast to many other popular options considered in the literature. In discussing this possibility, we also address some recent criticisms concerning the possibility of such running. Our conclusion is that, while there is no comprehensive proof of the CC running, there is no proof of the non-running either. The problem can be solved only through a deeper understanding of the vacuum contributions of massive quantum fields on a curved spacetime background. We suggest that such investigations are at the heart of one of the most important endeavors of fundamental theoretical cosmology in the years to come.

18 pages, LaTeX. Shortened and modified version of arXiv:0808.0315, accepted for publication in Physics Letters B. Section 4 include our complete refutation of the criticisms from the authors of arXiv:0712.3040 [hep-th]. Section 5 includes more detailed discussion of the possible form of effective action of gravity corresponding to the running of vacuum energy

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