Explorations in quantum theory of our accelerating Universe

by Dr Vasileios Letsios (University of Mons, Belgium)

Thursday 5 Feb 2026, 11:00 → 12:00 Europe/Athens

Astronomical observations indicate that our Universe experienced a phase of rapid accelerated expansion during its early inflationary epoch, and that it is currently entering a second period of acceleration driven by a small positive cosmological constant. Understanding the physics of an accelerating Universe—described by de Sitter (dS) spacetime—therefore requires studying Quantum Field Theory (QFT) directly in this spacetime.

In this seminar, I will summarise my research program on the application of quantum theory to dS spacetime. I will highlight the conceptual and technical surprises that arise when applying standard tools of QFT in dS, including an enriched particle spectrum with exotic properties absent in Minkowski space. I will also explain how information relevant to observables of early-Universe cosmology can be extracted within this framework. I will then turn to the problem of quantum gravity in dS spacetime. While methods from string theory are largely ineffective in dS, recent developments in holography and the gravitational path integral provide new avenues for constraining the structure of a consistent theory of dS quantum gravity. Taken together, these results point toward a more refined theoretical framework for understanding the quantum physics of cosmic acceleration.

 

Videoconference via     https://us02web.zoom.us/j/82249348474