February 25th 2026, @IEM/CSIC

IEM Conference Room. 

C/ Serrano 121. 28006. (Madrid)

11:30h     First Talk

Speaker: Kasia Rejzner   (York University, UK)

Title: QRFs, measurement, and the type of algebras in QFT

Abstract: Algebraic quantum field theory (AQFT) describes quantum fields in terms of nets of operator algebras associated with spacetime regions. However, the interpretation of observables and measurements becomes subtle in the presence of symmetries, where one recognizes that any physical measurement is performed relative to a reference system. I will argue that incorporating QRFs naturally leads to non-local, but operationally meaningful, observables. Notably, as a von Neumann algebra, the resulting structure could have dramatically different properties, which was showcased in the paper of Chandrasekaran, Longo, Penington and Witten about QFT coupled to an observer in de Sitter spacetime. I will report on recent results motivated by that work obtained in collaboration with Fewster, Janssen, Loveridge and Waldron.

15:00h     Second Talk

Speaker: Juan García-Bellido  (IFT-UAM/CSIC)

Title: General Relativistic Entropic Acceleration (GREA) Theory: Cosmic Acceleration from First Principles

Abstract: In this talk I will describe the GREA Theory of Dark Energy and its observational consequences for the late universe. I will compare against LCDM with the ACT+Planck18 CMB, DESY6+DESI-DR2 BAO and Pantheon+DESY5 SN data.