How do quantum models handle time travel?

Dissenting analyses focus less on whether the equations can generate consistent answers and more on what those equations assume. Critics argue that Deutschian consistency may require a special ontology of interacting parallel worlds, while philosophical and technical objections question whether the models preserve standard quantum principles or genuinely describe spacetime time travel. These critiques do not supply a settled replacement, but they challenge the interpretation of formal consistency as physical possibility.

• A philosophical critique argues that Deutsch’s model implicitly relies on interacting parallel worlds beyond the ontology of standard Everettian quantum mechanics.
• Critics of Deutsch’s model argue that solving paradoxes mathematically does not by itself establish that the required closed timelike curves or interpretation exist physically.
• Postselected models have faced proposed paradoxes and objections about their handling of interactions, although their proponents argue that a more complete analysis removes the alleged contradiction.
• Alternative quantum formulations can impose self-consistency or probabilistic future outcomes, but these are model-dependent resolutions rather than experimentally confirmed mechanisms for changing the past.

5 sourcesView sources