The status and prospects of quantum non-local field theory

Гарий Владимирович Ефимов

Guo Chuan Thiang

Bell correlations are the hallmark of quantum non-locality, and a rich context for analysing them is provided by the algebraic approach to quantum field theory (AQFT): the basic idea is to associate with each bounded region O of Minkowski spacetime an algebra A(O) of operators, of which a self-adjoint element P ∈ A(O) represents a physical quantity pertaining to that part of the field system lying in O, that is measurable by a procedure confined to O. The violation of Bell inequalities in AQFT is known to be "generic", as regards the choices of regions O, and of quantities P, and of states. Furthermore, they are typically "maximal" and "indestructible" in a sense that can be made mathematically precise. The prospects for “peaceful coexistence” between quantum non-locality and relativity theory’s requirement of no action-at-a-distance are also explored. The purpose of this Essay is to review the developments in these areas.

孟大中

Joseph Samper Finberg

Locally covariant algebraic quantum field theory (LCQFT) satisfies Einstein causality through microcausality and operational no-signalling, yet Bell-type correlations persist in entangled field states across spacelike regions. We demonstrate that this apparent tension reflects a fundamental covariance obstruction: no assignment of classical past variables can simultaneously be covariant under spacetime embeddings, screen off quantum correlations, and reproduce AQFT statistics. This obstruction is distinct from dynamical nonlocality or signalling violations. We formalize this as a no-go theorem in the category-theoretic framework of LCQFT, showing that Bell's notion of local causality -- requiring factorization conditioned on a common past -- is structurally incompatible with diffeomorphism covariance. The failure of Bell locality thus reflects not a breakdown of relativistic causality but the impossibility of embedding quantum correlations into a classical causal framework without introducing preferred foliations or non-covariant beables. This clarifies the conceptual status of nonlocality in relativistic quantum theory.

I.I. Popov, А. У. Бахадуров, Н. С. Вашурин +4 more

The results of the study of the polarization properties of the stimulated photon echo (SPE) excited at room temperature on free excitons and exciton states localized on surface defects of textured thin films are reported. The results of observation and investigation of the effect of the non-Faraday rotation of a femtosecond SPE in a textured thin film are presented. The physical processes occurring under the Faraday effect and the effect of the non-Faraday rotation of the photon echo (PE) polarization plane are compared.

M. K. Volkov, Гарий Владимирович Ефимов