Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Causality in quantum electrodynamics

M. I. Shirokov

Published May 1, 1976• 2 citations
OpenAlex

Abstract

Causality, in the sense of finiteness of the velocity of propagation of signals, is discussed for quantum electrodynamics. The paper proposes an appropriate quantum-mechanical criterion for causality. According to this criterion local observables like the field strengths E(x), H(x) and the current density j/sub ..mu../(x) behave causally. However, the theory contains quantities (like the electron number density) which exhibit macroscopic acausality. The reason for this result is discussed in a theory where the usual causality condition, i.e., local commutativity of the operators A/sub ..mu../ and psi, is satisfied. (AIP)

Related papers

Signal velocity in quantum electrodynamics

M. I. Shirokov

The fulfillment in quantum electrodynamics of the principle of relativistic causality—the signal velocity does not exceed the velocity of light—is discussed. In Sec. 1 it is argued that this principle is not guaranteed automatically merely by the local commutativity of the theory. Section 2 is a critical review of the signal transmission problems which have been formulated and solved in the literature. In Sec. 3, this problem is considered in the framework of a simple but fairly realistic model of quantum electrodynamics. The signal source is an external current localized in some region S. The arrival of a signal in a region D at a distance R is established by a change in the coordinate, momentum, or energy of a charged particle. It is shown that proof of relativistic causality of the theory requires one to take into account appropriately quantum-mechanical and, in particular, quantum-electrodynamical features of the problem. In the final fourth section, a general formulation and exact solution of the signal transmission problem are given. The treatment is of sufficient generality for one to be able to assert that in the framework of quantum electrodynamics none of the possible methods of signal transmission violate relativistic causality.

Soviet Physics Uspekhi•Apr 30, 1978•39 citations

Particle localization and the Notion of Einstein Causality

Gerhard C. Hegerfeldt

The notion of Einstein causality, i.e. the limiting role of the velocity of light in the transmission of signals, is discussed. It is pointed out that Nimtz and coworkers use the notion of signal velocity in a different sense from Einstein and that their experimental results are in full agreement with Einstein causality in its ordinary sense. We also show that under quite general assumptions instantaneous spreading of particle localization occurs in quantum theory, relativistic or not, with fields or without. We discuss if this affects Einstein causality.

arXiv:quant-ph/0109044•Sep 10, 2001•11 citations

Localization of particles, spreading and the notion of Einstein causality

Gerhard C. Hegerfeldt

The notion of Einstein causality, i.e. the limiting role of the velocity of light in the transmission of signals, is discussed. We show that under quite general assumptions instantaneous spreading of particle localization occurs in quantum theory, relativistic or not, with fields or without. We discuss if this affects Einstein causality. It is also pointed out that the controversy about recent experiments of Nimtz and coworkers reporting superluminal signal velocities in micro-wave tunneling arise from an indiscriminate use of terminology and that the experimental results are in full agreement with Einstein causality in its ordinary sense.

AIP conference proceedings•Jan 1, 2001•1 citation

On the violation of causality in relativistic quantum mechanics

Piotr Kosiński, Paweł Maślanka

The estimates on causality violating part of the wave function are given. The problem of acausal behavior of charge and current densities is discussed.

Journal of Mathematical Physics•Jul 1, 1990•5 citations

Causality and chance in relativistic quantum field theories

Richard Healey

Bell appealed to the theory of relativity in formulating his principle of local causality. But he maintained that quantum field theories do not conform to that principle, even when their field equations are relativistically covariant and their observable algebras satisfy a relativistically motivated microcausality condition. A pragmatist view of quantum theory and an interventionist approach to causation prompt the reevaluation of local causality and microcausality. Local causality cannot be understood as a reasonable requirement on relativistic quantum field theories: it is unmotivated even if applicable to them. But microcausality emerges as a sufficient condition for the consistent application of a relativistic quantum field theory.

arXiv:1405.3254•May 13, 2014•0 citations

Causality and communication in physics

Pierre Uzan

Understanding the concept of causality is fundamental in physics, as it conditions the very possibility of any exchange of information between physical systems. This article examines and compares three main interpretations of the correlative operational concept of "causal separation" that have been respectively proposed in special relativity, quantum theory, and according to the statistical "non-signalling" condition. These interpretations, which can be classified regarding the range of CHSH correlation degrees they allow, lead to radically different results regarding the exchange of information between physical systems. Namely, it can be shown that, in opposition with the non-communication theorem of quantum theory, non-local communication can be established between the two entangled parts of a physical system when the relativistic criterium of causal separation is satisfied but not the quantum one.

•Jan 1, 2026•0 citations
Causality, in the sense of finiteness of the velocity of propagation of signals, is discussed for quantum electrodynamics. The paper proposes an appropriate quantum-mechanical criterion for causality. According to this criterion local observables like the field strengths E(x), H(x) and the current density j/sub ..mu../(x) behave causally. However, the theory contains quantities (like the electron number density) which exhibit macroscopic acausality. The reason for this result is discussed in a theory where the usual causality condition, i.e., local commutativity of the operators A/sub ..mu../ and psi, is satisfied. (AIP)
The fulfillment in quantum electrodynamics of the principle of relativistic causality—the signal velocity does not exceed the velocity of light—is discussed. In Sec. 1 it is argued that this principle is not guaranteed automatically merely by the local commutativity of the theory. Section 2 is a critical review of the signal transmission problems which have been formulated and solved in the literature. In Sec. 3, this problem is considered in the framework of a simple but fairly realistic model of quantum electrodynamics. The signal source is an external current localized in some region S. The arrival of a signal in a region D at a distance R is established by a change in the coordinate, momentum, or energy of a charged particle. It is shown that proof of relativistic causality of the theory requires one to take into account appropriately quantum-mechanical and, in particular, quantum-electrodynamical features of the problem. In the final fourth section, a general formulation and exact solution of the signal transmission problem are given. The treatment is of sufficient generality for one to be able to assert that in the framework of quantum electrodynamics none of the possible methods of signal transmission violate relativistic causality.
The notion of Einstein causality, i.e. the limiting role of the velocity of light in the transmission of signals, is discussed. It is pointed out that Nimtz and coworkers use the notion of signal velocity in a different sense from Einstein and that their experimental results are in full agreement with Einstein causality in its ordinary sense. We also show that under quite general assumptions instantaneous spreading of particle localization occurs in quantum theory, relativistic or not, with fields or without. We discuss if this affects Einstein causality.
The notion of Einstein causality, i.e. the limiting role of the velocity of light in the transmission of signals, is discussed. We show that under quite general assumptions instantaneous spreading of particle localization occurs in quantum theory, relativistic or not, with fields or without. We discuss if this affects Einstein causality. It is also pointed out that the controversy about recent experiments of Nimtz and coworkers reporting superluminal signal velocities in micro-wave tunneling arise from an indiscriminate use of terminology and that the experimental results are in full agreement with Einstein causality in its ordinary sense.
Bell appealed to the theory of relativity in formulating his principle of local causality. But he maintained that quantum field theories do not conform to that principle, even when their field equations are relativistically covariant and their observable algebras satisfy a relativistically motivated microcausality condition. A pragmatist view of quantum theory and an interventionist approach to causation prompt the reevaluation of local causality and microcausality. Local causality cannot be understood as a reasonable requirement on relativistic quantum field theories: it is unmotivated even if applicable to them. But microcausality emerges as a sufficient condition for the consistent application of a relativistic quantum field theory.
Understanding the concept of causality is fundamental in physics, as it conditions the very possibility of any exchange of information between physical systems. This article examines and compares three main interpretations of the correlative operational concept of "causal separation" that have been respectively proposed in special relativity, quantum theory, and according to the statistical "non-signalling" condition. These interpretations, which can be classified regarding the range of CHSH correlation degrees they allow, lead to radically different results regarding the exchange of information between physical systems. Namely, it can be shown that, in opposition with the non-communication theorem of quantum theory, non-local communication can be established between the two entangled parts of a physical system when the relativistic criterium of causal separation is satisfied but not the quantum one.