2005/11/30 by Nemanja Kaloper, Lorenzo Sorbo
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #astro-ph #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1088/1475-7516/2006/04/007
published as JCAP 0604:007,2006 · 16 pages, 1 figure
arxiv created 2005/12/06 · openalex publication_date 2006/04/19 · arxiv updated 2009/12/01 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/31
We review the pNGB quintessence models, and point out that the reason why the large decay constants are really needed is to tame a tachyonic instability present for a wide range of initial vev s. Starting very close to potential maxima does not help because quantum fluctuations during early inflation at a scale H I perturb the quintessence vev , displacing it from the maxima. This issue is quite interesting for pNGB dark energy in light of the recently discussed difficulties with embedding models with f a > M Pl in fundamental theory. A possible way around is provided by models with several ultralight pNGBs, which can drive a short burst of very late inflation together even if all of their decay constants obey f a < M Pl . Starting with their vev ∼ f a , the pNGBs will hold each other up on the potential for a longer time period. Their effective dynamics is captured by a collective mode, containing admixtures of all of the rolling pNGBs, which behaves as an ultralight field with f eff > M Pl . We point out that there may be potentially observable large scale disturbances in the sea of dark energy in such models.