This paper deals with the Newton–Wigner position observable for Poincaré-invariant classical systems. We prove an existence and uniqueness theorem for elementary systems that parallels the well-known Newton–Wigner theorem in the quantum context. We also discuss and justify the geometric interpretation of the Newton–Wigner position as “center of spin”, already proposed by Fleming in 1965 again in the quantum context.

中文翻译：

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关于可观测牛顿-维格纳位置的经典观点

本文处理 Poincaré 不变经典系统的可观察到的 Newton-Wigner 位置。我们证明了基本系统的存在性和唯一性定理，该定理与量子环境中著名的牛顿-维格纳定理相似。我们还讨论并证明了牛顿-维格纳位置作为“自旋中心”的几何解释，这已经由弗莱明在 1965 年再次在量子背景下提出。