# Progress and Visions in Quantum Theory in View of Gravity: Bridging foundations of physics and mathematics

## Discussion sessions

The conference consisted of talks and discussion sessions. The following topics have been discussed among all participants in plenary or parallel sessions of 60 minutes each.

- Conceptual significance and experimental possibilities of Quantum Field Theory beyond scattering theory
- Which mathematical and physical structures of Quantum Field Theory are believed to transcend the gravity-quantum unification
- The role of observables in Quantum Gravity in light of diffeomorphism invariance and quantization
- Axiomatization of Quantum Field Theory: Will practical Quantum Field Theory one day be replaced by a proper mathematical framework with axiomatizable foundations?
- A critical assessment of current approaches to Quantum Gravity concerning unification
- Theory-experiment wishlist: What is most urgently needed by one side from the other in order to make progress?
- Do we really have a fundamental understanding of ordinary matter? Can Quantum Mechanics be derived from Quantum Field Theory?
- Does gravity play a role when considering interpretations or modifications of Quantum Theory?
- Guiding questions for the next generation
- Which problems and which opportunities would arise if gravity were fundamentally classical?
- Unification wish list: What questions do we hope/expect/demand a fundamental theory to answer? What is a checklist for a new unified theory?
- What cherished physical principles are you most willing to give up, and why, if Quantum Gravity won't allow them all?
- Nature of Time (Is time fundamental? What mathematical structure could time have?)
- What is the meaning of probabilities in physical theories where properties/events do not repeat themselves?
- What is the microscopic structure of spacetime? If spacetime were fundamentally discrete, what would be the macroscopically observable implications?
- Tabletop/low energy experiments for probing gravitational effects in quantum systems
- Must spacetime singularities be resolved in Quantum Gravity? Will new insights into the causal structure of quantum spacetime shift the focus in studying black holes?
- To what extent do the rigorous proofs of mathematical results in Quantum Field Theory contribute to our "understanding" of those results?
- Is Quantum Field Theory in a classical external field (gravitational or electromagnetic) well understood conceptually and mathematically?
- What is the measurement problem in Quantum Field Theory?
- What is the significance of a global state? Is global hyperbolicity a necessary condition for consistent Quantum Field Theory?
- What counts as "understanding" in Quantum Mechanics and Quantum Field Theory?
- Does gravitational entanglement imply that gravity is quantum? (And if yes, may it inform specific Quantum Gravity Theories?)
- Quantum Causal Indefinite Structures and Quantum Field Theory - Mutual inspirations and conflicting concepts
- New experimental paradigms at the interface of Quantum Mechanics, Quantum Field Theory and gravity which are currently controversial or go beyond what has been published so far
- Ideas for innovative formats of conferences: How can we communicate more efficiently and understand more?
- Which visions do senior scientists have for the future? What could senior scientists learn from juniors?
- What you always wanted to ask/know/clarify?

## Date and Location

**October 01 - 05, 2018**

Max Planck Institute for Mathematics in the Sciences

Inselstraße 22

04103 Leipzig

Germany

see travel instructions

## Scientific Organizers

**Felix Finster**, University of Regensburg, Regensburg (Germany)**Domenico Giulini**, University of Hanover (Germany)**Johannes Kleiner**, University of Hanover (Germany)**Jürgen Tolksdorf**, MPI for Mathematics in the Sciences, Leipzig (Germany)

## Administrative Contact

**Antje Vandenberg**

MPI for Mathematics in the Sciences

Leipzig (Germany)

Contact by Email