Ivonne Zavala: Is Dark Energy Evolving? A String Theory Perspective

Tuesday 3 Nov 2026, 13:15 → 15:15 Europe/Stockholm

FB42 (AlbaNova Main Building)

Recent cosmological analyses have revived the interest in dynamical dark energy, showing hints of evolution at roughly the 3-sigma level. This makes it a good moment to ask what string theory can, and cannot, currently say about dark energy. I will review the status of de Sitter vacuums (constant dark energy) and explore how steep, rolling fields (quintessence) emerge as a natural alternative. I will also discuss the data's intriguing preference for a phantom-like crossing of w = -1, which may point toward couplings in the dark sector, a feature naturally present in string models, though accompanied by significant theoretical challenges. Since fundamental theory has not yet delivered a definitive mechanism, we can look to data-driven approaches for guidance. I will introduce how symbolic regression—an interpretable machine learning technique—can search cosmological data directly for explicit, simple expressions for the scalar potentials or the dark energy equation of state.

About the speaker: I am a theoretical cosmologist at Swansea University, having done my PhD at Cambridge and postdoctoral research in Europe and the US. My research lies at the interface of string theory, cosmology and gravitational physics, connecting fundamental theory with observable signatures of the early and late Universe. My work spans inflation, dark energy, dark sectors and gravitational-wave cosmology, including applications to LISA, the Einstein Telescope and pulsar timing arrays. More recently, I have been applying symbolic regression to cosmology, using theoretical input to reconstruct dark-energy potentials and equations of state in modified gravity and string-motivated models.

At the OKC: Tuesday Nov 3rd (full day)