Description
Scalar fields are ubiquitous in string theory compactifications, arising
from geometric moduli and as descendants of higher-dimensional form fields. In
cosmology, they provide well-motivated frameworks for dynamical dark energy and
interacting dark sectors, allowing for time-varying equations of state and an
effective phantom behaviour, features that have recently attracted attention in
connection with late-time deviations from ΛCDM. In this talk I will present recent
progress on single- and multi-scalar dark-energy models, and their cosmological
implications within a theoretically consistent framework. I will highlight how
theoretical limitations may shape the space of viable models and where new
dynamics may remain possible. I will also comment on how reconstruction
approaches, including modern data-driven techniques, may help connect
theoretical constraints to emerging observational trends.
