A Non-causal Reconceptualization of Quantum Field Theory

Da Wei

The classical framework of causality faces a significant theoretical impasse. Cartesian dualism introduces a profound interaction problem regarding mind and matter, while traditional physical models struggle to accommodate the epistemic observer. Because linear causal chains fail to fully explain the dynamic act of observation, this paper proposes a fundamental reconceptualization of causal structure. By firmly grounding our approach in quantum entanglement theory, specifically utilizing the Greenberger-Horne-Zeilinger (GHZ) multi-body entanglement properties, we argue that causality inherently requires a strict triadic architecture. This triad comprises an Observer, an active Medium, and an Observed target. Quantum nonlocality suggests that fundamental causality extends beyond strict local interactions, a principle illustrated mathematically and ontologically by the GHZ state. Removing any single entity within this system collapses the coherent network, indicating that the medium serves as an active participant enforcing topological constraints rather than a passive background. Furthermore, this necessity for triadic structure scales universally across physical theory: special relativity's light-cone causality eliminates instantaneous two-body interaction, quantum field theory's interaction Lagrangian encodes all forces as three-point vertices, and gauge theory's local symmetry requirements necessitate intervening gauge fields. Ultimately, this framework provides a logically consistent and physically grounded perspective on the classical mind-matter interaction problem, framing causation as information flowing within an irreducible triadic network.

Damiano Anselmi

Jan Mandrysch, R. Simmons, Miguel Navascués

As noted by Sorkin, regarding quantum instruments whose Kraus operators are localizable within some spacetime region as operations accessible therein leads to superluminal communication. This so-called Sorkin paradox can be resolved by further constraining the set of allowed local operations in quantum field theory (QFT). In this spirit, Fewster and Verch proposed a framework for local QFT operations that generalizes non-relativistic quantum measurement theory and does not lead to Sorkin-like paradoxes. Shortly afterwards, Jubb (and later Oeckl) identified the minimal conditions that QFT instruments must satisfy to be compatible with Einstein's causality. In this work, we study both approaches in the quantum field theory of the free scalar field. First, we prove that a very wide class of causal instruments is FV-realizable: namely, those whose measurement channels are random displacements of the field operators. As we show, this class allows implementing arbitrary instruments in a heralded, probabilistic way, as well as non-demolition measurements deterministically. Second, we construct examples of causal channels that do not admit an approximate FV realization. Some of such causal, not FV-realizable channels violate basic physical principles, so they should not be part of any measurement theory for QFT. Third, we investigate the difficulty of characterizing the set of QFT channels that can be generated through the composition of several FV schemes. In this regard, we find a countable family of simple QFT channels for which no Turing machine can discriminate between channels within or far away from the implementable set.

P. N. Kaloyerou

L. A. Khalfin

Hans H. Diel

The non-localities in quantum theory (QT) (the most famous example is expressed in the violation of Bell's inequality in experiments) impede the construction of a local causal model of QT including quantum field theory (QFT).The laws of collective behavior may be considered to be types of non-local laws: laws that apply to the collection of system components as a whole.The article presents a proposal for the treatment of the non-localities that exist in QT/QFT by the concepts of collective behavior.The basic components of the collective behavior are the spatial elements of the causal model of QT/QFT proposed by the author.