  Motivated by the swampland conjectures, we study cosmological signatures of a
quintessence potential which induces time variation in the low energy effective
field theory. After deriving the evolution of the quintessence field, we
illustrate its possible ramifications by exploring putative imprints in a
number of directions of particle phenomenology. We first show that a dark
matter self-interaction rate increasing with time gives a novel way of
reconciling the large self interactions required to address small scale
structure issues with the constraint coming from clusters. Next, we study the
effects of kinetic mixing variation during the radiation dominated era on
freeze-in dark matter production. Last, we elucidate quintessence effects on
the restoration of the electroweak symmetry at finite temperature and the
lifetime of the electroweak vacuum through a modification of the effective
Higgs mass and quartic coupling.
