Quantum gravity is a gauge theory with the gauge symmetry spacetime diffeomorphisms. Presumably the quantum state of our universe is invariant under spacetime diffeomorphisms, including timelike ...
Does a complete theory of quantum gravity require anthropic post-selection? Certainly the black hole complimentarity and causal patch conjectures highlights the essential role of observers, at least ...
This number is thrown around a lot so I'd like to understand its origin. I know that it counts compactifications of string theories on (not only) Calabi-Yau manifolds and probably also some other ...