Time Symmetry, Retrocausality and the Emergent: Arrow of Time the Quantum Time-Symmetric Interpretation (QTSI)

Abstract

Microscopic quantum laws are time-symmetric: nothing in the Schr\"odinger equation or its relativistic extensions distinguishes future from past. Yet measurements produce irreversible records, an apparently one-way causal flow, and the familiar notion that causes precede effects. Within the Quantum Time-Symmetric Interpretation (QTSI), this asymmetry is not fundamental but emergent. Isolated quantum systems are described by a two-component temporal state containing forward- and backward-propagating amplitudes. Their mixing, governed by a parameter $\Delta(\phi)$, defines a retrocausal coherence time $\tau_{RC}(\phi)$ beyond which advanced components are suppressed. As the system couples to amplifying environments characterized by a macroscopic parameter $\phi$, $\Delta(\phi)$ decreases and the backward component is dynamically eliminated, giving rise to classical causality and effective collapse. QTSI aligns naturally with time-symmetric approaches from Wheeler--Feynman, Aharonov, and Price, agrees with all weak-measurement and quantum eraser results in their operational regimes, and predicts specific signatures in temporal echoes and chaotic cavities. Detailed formal and experimental developments appear in the Supplementary Addenda.