On Causality in Nonlocal Field Theory

Luciano Maiani, M. Testa

Alexander A. Chernitskii

The problems connected with a causality of space-time universe and with the paradox of Einstein, Podolsky, and Rosen are considered. A main philosophical problem and its possible solutions are briefly discussed. A concept of unified local field theory is considered. It is shown that in the framework of such theory there are nonlocal correlations between space separate events. These correlations are predicted by quantum mechanics and they are confirmed by Aspect type experiments for testing of Bell inequality. The presence of these nonlocal correlations in the framework of a local field theory is connected with the fact that its solution is nonlocal in character. Prospects for possible applications of an unified local field theory are considered.

G. Compagno, G. Massimo Palma, Roberto Passante +1 more

Matthew J. Lake

This article reviews six historically important papers in the development of the theory of measurement for nonlocal variables in quantum mechanics, with special emphasis the non violation of relativistic causality. Spanning more than seventy years, we chart the major developments in the field from the declaration, by Landau and Peierls in 1931, that measurement of nonlocal variables was impossible in the relativistic regime to the demonstration, by Vaidman in 2003, that all such variables \emph{can} be measured instantaneously without violation of causality through an appropriate act of "measurement", albeit not of a standard projective (Von Neumann) type.

N. N. Bogolyubov

Eduardo Gonzalez-Granda Fernandez

This work investigates structural constraints on hidden-variable extensions of relativistic quantum field theory imposed by analyticity and the spectral condition. Building on a previously established no-go theorem for causally localized modifications, we analyze relativistic Bohmian quantum field theories, focusing on the multi-time framework developed by Hrvoje Nikolić. We show that any hidden-variable extension preserving Wightman analyticity cannot be represented as a localized spacetime modification of correlation functions. Instead, viable theories must abandon spacetime localization and exhibit intrinsically nonlocal structures defined on configuration space. This provides a structural explanation for the nonlocal character of Bohmian quantum field theories and clarifies the distinction between strong (distributional) localization and weak (operational) localization. The paper also proposes a classification of nonlocal hidden-variable models and explores connections with causal-model approaches to quantum correlations.