Abstract
We revisit the phenomenology of quintessence models in light of the recently refined version of the de Sitter Swampland conjecture, which includes the possibility of unstable de Sitter critical points. We show that models of quintessence can evade previously derived lower bounds on (1 + w), albeit with very finely-tuned initial conditions. In the absence of such tuning or other rolling quintessence fields, a field with mass close to Hubble is required, which has a generic prediction for (1+ w). Slow-roll single field inflation models remain in tension. Other phenomenological constraints arising from the coupling of the quintessence field with the Higgs or the QCD axion are significantly relaxed.
Highlights
The refined de Sitter conjecture (RdSC) is motivated by its connection to the distance Swampland conjecture [3] through Bousso’s covariant entropy bound [48]
In this note we investigate the implications of the refined de Sitter conjecture (RdSC) for dark energy phenomenology
We show that the RdSC allows a class of models where the quintessence field satisfies the second clause of the refined conjecture, and we cannot put a bound on c using data
Summary
Dark energy observations allow a quintessence field in the current universe with a potential whose slope is of the order of the vacuum energy (in Planck units). If the quintessence does not couple to the Higgs, the dSC is badly violated at the symmetric point of the Higgs potential [42]. At the symmetric point on the Higgs potential the RdSC is satisfied irrespective of the coupling of the Higgs with the quintessence field. The gradient of the potential is sufficiently large even away from the minimum (and well into the region where |∇hV | is large), if the following condition is met for the potential at h = v,. This is a very mild restriction on the potential. The RdSC can be consistent with these constructions if the smallest eigenvalue of the Hessian is sufficiently negative at these critical points
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