Of pNGB QuiNtessence

Nemanja Kaloper; Lorenzo Sorbo

doi:10.1088/1475-7516/2006/04/007

paper

Of pNGB QuiNtessence

arXiv:astro-ph/0511543 · doi:10.1088/1475-7516/2006/04/007

Abstract

We review the pNGB quintessence models, and point out that the reason why the large decay constants $f_a \ga {\cal O}(1)M_{Pl}$ are really needed is to tame a tachyonic instability present for a wide range of initial $v e v$ s. Starting very close to potential maxima does not help because quantum fluctuations during early inflation at a scale $H_{I}$ perturb the quintessence $v e v$ , 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 $f_{a} > M_{P l}$ 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 {\it together} even if all of their decay constants obey $f_{a} < M_{P l}$ . Starting with their $v e v \sim f_{a}$ , 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 $f_{e f f} > M_{P l}$ . We point out that there may be potentially observable large scale disturbances in the sea of dark energy in such models.

arXiv comment16 pages, 1 figure

Of pNGB QuiNtessence

Abstract

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