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### Retrocausality & TGD

#### Abstract

This article is inspired by the article "Is a time symmetric interpretation of quantum theory possible without retrocausality?" of Leifer and Pusey related to the notion of retrocausality. Retrocausality means the possibility of causal influences propagating in non-standard time direction. The conjecture is that retrocausality could allow wave functions to be real and allow to get rid of the problematic notion of state function reduction. TGD leads to a new view about reality of wave function solving the basic problem of quantum measurement theory. In ZEO quantum states are replaced by zero energy states analogous to pairs of initial and final states in ordinary positive energy ontology and can be regarded as superpositions of classical deterministic time evolutions. The sequence of state function reductions means a sequence of re-creations of the superpositions of classical realities identified as space-time surfaces. The TGD based view about scattering amplitudes has rather concrete connection with the view of Cramer as I interpret it. There is however no attempt to reduce quantum theory to a purely classical theory. The notion of the "world of classical worlds" (WCW) consisting of classical realities identified as space-time surfaces replaces space-time as a fixed observer independent reality in TGD. Retrocausality is basic aspect of TGD. Zero Energy Ontology (ZEO) predicts that both arrows of time are possible. In this sense TGD is time symmetric. On the other hand, twistor lift of TGD predicts a violation of time reflection

*T*and this might imply that second arrow of causality dominates in some sense. The ZEO based view about state function reduction essential for TGD inspired theory of consciousness and implying generalized Zeno effect giving rise to conscious entities - "selves" - is also essential. One might say that when conscious entity dies it re-incarnates as time-reversed self.