Renata Ferrero, Kristina Giesel, Muxin Han
May 2025
FAU² Workshop: Quantum Gravity Across Scales at FAU Erlangen Nuremberg
The “FAU² Workshop on quantum gravity across scales: from physics at the Planck scale to effective theories” was held from 20–22 May 2025, at the ECAP (Erlangen Center for Astroparticle Physics) Laboratory in Erlangen, Germany. The event gathered over 30 participants in person and 20 more online, creating a vibrant environment for discussions on the interplay between quantum gravity approaches at the Planck scale and their corresponding low-energy effective descriptions. It brought together experts in canonical and covariant loop quantum gravity (LQG), group field theory (GFT), string theory and asymptotically safe gravity, fostering dialogue across different frameworks.This was the third workshop jointly organized by Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and Florida Atlantic University (FAU). The workshop format prioritized collaboration: mornings were reserved for informal discussions and joint work, while afternoons featured structured talks and thematic sessions. This year’s program included contributed talks and a poster session, offering early-career researchers a platform to present their work
The workshop was organized into six thematic sessions, covering both foundational aspects of quantum gravity and applied topics, including cosmology, black hole physics, and relational/quantum reference frames. Some highlights were the role of effective theories accessed via the renormalization group, effective models of quantum cosmology and LQG-inspired phenomenological models, black hole physics and collapse scenarios in the context of asymptotic safety and LQG-inspired effective models, foundational questions about holography, group field theory, effective spin foams, quantum reference frames and dressed observables, the algebra of observables and quantum field theory, and recent results on perturbation theory in black hole spacetimes. Each session was complemented by contributed presentations, whose work enriched the discussions and brought fresh perspectives on all covered topics. For further details please visit the website of the workshop.
The day’s talks concluded with discussion sessions focused on the session's themes. These discussions were particularly fruitful in clarifying semantic ambiguities, especially around the notion of “effective” across different approaches. Participants shared challenges, explored opportunities for cross-framework connections, and debated possible challenges and future steps for quantum gravity approaches in the context of black holes and cosmology.
Social events, including a welcome reception and a barbecue dinner, extended the scientific conversations in a relaxed atmosphere, that, among other options, also included Bavarian beer and traditional bavarian sausages.