Home › Forums › 2015 International Workshop on Quantum Foundations › Retrocausal theories › Quantum causal models, faithfulness and retrocausality (onl. 7/16 @ 11pm UTC+10) › Reply To: Quantum causal models, faithfulness and retrocausality (onl. 7/16 @ 11pm UTC+10)
The argument that retrocausality in a block universe violates faithfulness is essentially reflected by an anonymous referee in footnote 3 of our paper https://ijqf.org/wp-content/uploads/2015/06/IJQF2015v1n3p2.pdf:
“I do not see how anything truly ‘retrocausal,’ in a dynamical sense, can occur given global time-symmetric constraints on spacetime. The authors seem to me to be too charitable here, a future boundary condition implies an adynamical block world, in which talk of dynamics or intervention is superfluous at best, and inconsistent at worst.”
We really need a direction for the undirected link in Evans’ Fig 4 to have “objective” causality. I think it’s best to view causality as a matter of perspective within the block universe (“subjective” causality per Price, as Evans explains). Given the 4D perspective of the block universe, an “objective” explanatory mechanism need not involve causation in “retro-time-evolved” form or otherwise, as we argue on pp 128-130 of our paper.
Thus, in RBW, we have proposed a formal counterpart to the “nomological dependence” of Hausman and the “non-causal dependency constraints” of Woodward that we call the adynamical global constraint (AGC). A paragraph explaining the AGC conceptually is on p 130 and a mathematical explanation is provided on pp 144-145. An application to the twin-slit experiment is on pp 146-154. The AGC brings Price’s Helsinki toy model with its “global constraints” to fruition.