Unitarity of evolution in quantum gravity

Ascertain whether unitary time evolution is a meaningful concept in non‑perturbative quantum gravity and, if not, develop a mathematically precise alternative (e.g., isometric evolution) that preserves inner products in a relational framework.

Background

The second panel examined foundational constraints such as unitarity, causality, and stability. In the context of canonical quantum gravity and relational time, the standard notion of unitary evolution was questioned.

The discussion highlighted that the Wheeler–DeWitt framework lacks an explicit time coordinate and may require reinterpreting evolution via relational observables, raising uncertainty over whether unitary evolution is even the right concept.