Can causal inequalities be violated when spacetime itself is superposed? · revision history
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Accepted · first revision · record
- Title
- Can causal inequalities be violated when spacetime itself is superposed?
- Plain
- Some theoretical processes give correlations that no fixed, or randomly chosen, order of events could explain; these violate causal inequalities. They cannot appear for events localized in an ordinary fixed spacetime; whether a spacetime in superposition, as quantum gravity may allow, can produce them is unknown.
- Precise
- Causal inequalities bound correlations $p(a,b\mid x,y)$ achievable when parties act in a definite or classically random order. With spacetime-localized operations in a fixed acyclic spacetime they cannot be violated (Vilasini and Renner, PRA 2024), and on time-delocalized subsystems they can (Wechs, Branciard, Oreshkov, Nat. Commun. 2023). Determine whether a violation by spacetime-localized operations is possible when the spacetime geometry itself is in superposition (a gravitating source mass in spatial superposition), and give the minimal source mass and coherence time for it.
- Settled by
- A proof that localized realizations are impossible even with superposed geometry, or an explicit physical protocol with a gravitating source in superposition achieving a violation.
- Kind
- well-posed
- Answer type
- yes-no
- References
- (empty)
- Literature status
- partially-resolved
- Status note
- Fixed-spacetime localized realizations are excluded (Vilasini and Renner, PRA 2024); time-delocalized realizations exist (Wechs et al., 2023); the dynamical-spacetime case is open.
- Posed since
- 2012