Problems about Causality in Fermi's Two-Atom Model and Possible Resolutions

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dc.creatorHegerfeldt, Gerhard C.
dc.date1997-07-07
dc.date.accessioned2026-07-07T06:14:20Z
dc.date.available2026-07-07T06:14:20Z
dc.descriptionIn order to check finite propagation speed Fermi, in 1932, had considered two atoms A and B separated by some distance R. At time t=0, A is in an excited state, B in its ground state, and no photons are present. Fermi's idea was to calculate the excitation probability of B. In a model-independent way and with minimal assumptions - Hilbert space and positive energy only - it is proved, not just for atoms but for any systems A and B, that the excitation probability of B is nonzero immediately after t=0. Possible ways out to avoid a contradiction to finite propagation speed are discussed. The notions of strong and weak Einstein causality are introduced.
dc.description13 pages, Latex
dc.identifierhttps://arxiv.org/abs/quant-ph/9707016
dc.identifierhttp://arxiv.org/abs/quant-ph/9707016
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/93425
dc.subjectQuantum Physics
dc.titleProblems about Causality in Fermi's Two-Atom Model and Possible Resolutions
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