Can the cosmological constant term run in Einstein's equations?

[wolram]

arXiv:0808.0315 (cross-list from hep-th) [ps, pdf, other]
Title: Can the cosmological "constant" run? - It may run
Authors: Ilya L. Shapiro, Joan Sola
Comments: LaTeX, 36 pages, extended discussion, typos corrected, references added. Sections 2 and 4 include our complete refutation of the criticisms from the authors of arXiv:0712.3040 [hep-th] against our previous papers on this subject
Subjects: High Energy Physics - Theory (hep-th); Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

Using standard quantum field theory, we discuss several theoretical aspects of the possible running of the cosmological constant (CC) term in Einstein's equations. The basic motivation for the present work is to emphasize that this possibility should also be taken into account when considering dynamical models for the dark energy (DE), which are nowadays mainly focused on identifying the DE with the energy density associated to one or more ad hoc scalar fields. At the same time, we address some recent criticisms that have been published (or privately communicated to us) attempting to cast doubts on the fundamental possibility of such running. In this work, we argue that while there is no comprehensive proof of the CC running, there is no rigorous proof of the non-running either. In particular, some purported "non-running theorem" recently adduced in the literature is, in our opinion, completely insubstantial and formally incorrect. The way to the CC running is, therefore, still open and we take here the opportunity to present a pedagogical review of the present state of the art in this field, including a a brief historical account.

 

[marcus]

Running Lambda (i.e. running CC) is a basic feature of several leading quantum gravity approaches. It plays a big role in Martin Reuter's approach. He uses it to explain some features of cosmology that don't have a very good explanation otherwise. And his approach wouldn't work without running Lambda.

Loll's Causal Triangulations approach also depends on having a positive Lambda and it has a "bare value" which I believe can be different from the observed value that you see at large scale. That is usually the case with running constants.

I looked at the Ilya Shapiro article, he cites a whole bunch of other people (as well as a Reuter paper) so I guess the idea of running Lambda is widespread, and must have been around for quite a while.

It seems to be shared by some quite different approaches.