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SPS Journal Club: ‘Hilltop quintessence, the LARGE Volume Scenario and varying-tension cosmic strings’
Recent observational data suggests that the dark energy equation of state parameter wDE is evolving with time, in apparent tension with the ΛCDM standard model of cosmology. Here we review these observational results, with particular emphasis on the evidence for phantom-like behaviour, for which wDE < −1. In an attempt to reproduce the data, we study a quintessence model of a single scalar field rolling down a hilltop potential, both from a UV-agnostic perspective and from a string theory point-of-view. For the latter we focus on a scalar potential derived from type IIB supergravity in the context of the LARGE Volume Scenario (LVS), and investigate the cosmological dynamics of the scalar near its maximum. Finally, we discuss whether an effective phantom behaviour can be reproduced by considering the interaction between the scalar field and cosmic strings with a time-dependent tension, while keeping the LVS scalar potential unchanged.