Can quantum gravity forbid time travel?

Lens adapted to this topic: Emergent-time and permissive possibilities

Dissenting and exploratory work emphasizes that arguments against time travel often presuppose a classical notion of time and a particular spacetime description. If spacetime and time emerge from deeper quantum structures, quantum gravity could alter how closed timelike curves are defined rather than simply forbid them. This remains a research programme, not an established result.

• Because many quantum-gravity approaches regard relativistic spacetime as emergent, their implications for closed timelike curves cannot be read off straightforwardly from classical general relativity.
• Arguments that logical or physical contradictions rule out time travel may rely on time concepts that are themselves problematic in quantum gravity.
• A philosophical-physics analysis stresses that proposed no-go theorems depend on how a time machine is defined and have not achieved sufficient generality.
• Some quantum-gravity approaches may forbid closed timelike curves outright, while others do not yet clearly address whether quantum states of geometry can contain them.

Featured sourceTime travelling in emergent spacetimearxiv.org4 sourcesView sources