{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T02:15:49Z","timestamp":1760148949940,"version":"build-2065373602"},"reference-count":64,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2023,6,12]],"date-time":"2023-06-12T00:00:00Z","timestamp":1686528000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>Everett\u2019s many-worlds or multiverse theory is an attempt to find an alternative to the standard Copenhagen interpretation of quantum mechanics. Everett\u2019s theory is often claimed to be local in the Bell sense. Here, we show that this is not the case and debunk the contradictions by analyzing in detail the Greenberger\u2013Horne\u2013Zeilinger (GHZ) nonlocality theorem. We discuss and compare different notions of locality often mixed in the Everettian literature and try to explain the nature of the confusion. We conclude with a discussion of probability and statistics in the many-worlds theory and stress that the strong symmetry existing between branches in the theory prohibits the definition of probability and that the theory cannot recover statistics. The only way out from this contradiction is to modify the theory by adding hidden variables \u00e0 la Bohm and, as a consequence, the new theory is explicitly Bell-nonlocal.<\/jats:p>","DOI":"10.3390\/sym15061250","type":"journal-article","created":{"date-parts":[[2023,6,13]],"date-time":"2023-06-13T01:35:30Z","timestamp":1686620130000},"page":"1250","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["An Elementary Proof That Everett\u2019s Quantum Multiverse Is Nonlocal: Bell-Locality and Branch-Symmetry in the Many-Worlds Interpretation"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8714-2981","authenticated-orcid":false,"given":"Aur\u00e9lien","family":"Drezet","sequence":"first","affiliation":[{"name":"Institut NEEL, CNRS and Universit\u00e9 Grenoble Alpes, F-38000 Grenoble, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Barrett, J.A., and Byrne, P. (2012). The Everett Interpretation of Quantum Mechanics: Collected Works 1955\u20131980 with Commentary, Princeton University Press.","DOI":"10.1515\/9781400842742"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"454","DOI":"10.1103\/RevModPhys.29.454","article-title":"\u2018Relative State\u2019 formulation of quantum mechanics","volume":"29","author":"Everett","year":"1957","journal-title":"Rev. Mod. Phys."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"777","DOI":"10.1103\/PhysRev.47.777","article-title":"Can quantum-mechanical description of physical reality be considered complete?","volume":"47","author":"Einstein","year":"1935","journal-title":"Phys. Rev."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Bell, J.S. (2004). Speakable and Unspeakable in Quantum Mechanics, Cambridge University Press. [2nd ed.].","DOI":"10.1017\/CBO9780511815676"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Kafatos, M. (1989). Bell Theorem, Quantum Theory and Conceptions of the Universe, Kluwer Academic.","DOI":"10.1007\/978-94-017-0849-4"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/0375-9601(82)90264-X","article-title":"The Einstein-Podolsky-Rosen physical reality is completely described by quantum mechanics","volume":"91","author":"Page","year":"1982","journal-title":"Phys. Lett. A"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1119\/1.3243279","article-title":"The EPR paradox, Bell\u2019s inequality, and the question of locality","volume":"78","author":"Blaylock","year":"2010","journal-title":"Am. J. Phys."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1086\/psaprocbienmeetp.1994.1.193026","article-title":"On the Paradoxical Aspects of New Quantum Experiments","volume":"1","author":"Vaidman","year":"1994","journal-title":"PSA Proc. Bienn. Meet. Philos. Sci. Assoc."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Bell, M., and Gao, S. (2015). Quantum Nonlocality and Reality, Cambridge University Press.","DOI":"10.1017\/CBO9781316219393"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"11281","DOI":"10.1073\/pnas.1324238111","article-title":"Quantum nonlocality does not exist","volume":"111","author":"Tipler","year":"2014","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_11","unstructured":"Lupacchini, R., and Fano, V. (2002). Understanding Physical Knowledge, Department of Philosophy, University of Bologna, CLUEB."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Bell, M., and Gao, S. (2015). Quantum Nonlocality and Reality, Cambridge University Press.","DOI":"10.1017\/CBO9781316219393"},{"key":"ref_13","unstructured":"Price, M.C. (2023, May 25). The Everett FAQ. Available online: https:\/\/www.hedweb.com\/everett\/."},{"key":"ref_14","unstructured":"Sakaguchi, T. (1996). On the EPR phenomenon. arXiv."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1759","DOI":"10.1098\/rspa.2000.0585","article-title":"Information flow in entangled quantum systems","volume":"456","author":"Deutsch","year":"1999","journal-title":"Proc. R. Soc. Lond. A"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"301","DOI":"10.1023\/A:1012357515678","article-title":"Locality in the Everett interpretation of Heisenberg-picture quantum mechanics","volume":"14","author":"Rubin","year":"2001","journal-title":"Found. Phys. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"869","DOI":"10.1007\/s10701-009-9300-2","article-title":"An introduction to many worlds in quantum computation","volume":"39","year":"2009","journal-title":"Found. Phys."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Brassard, G., and Raymond-Robichaud, P. (2019). Paralell lives: A local-realistic interpretation of \u201cnonlocal\u201d boxes. Entropy, 21.","DOI":"10.3390\/e21010087"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"272","DOI":"10.3390\/quantum3020017","article-title":"The ABC of Deutsch-Hayden descriptors","volume":"3","year":"2021","journal-title":"Quantum Rep."},{"key":"ref_20","first-page":"39","article-title":"Reformulating Bell\u2019s theorem: The search for a truly local quantum theory","volume":"70","author":"Waegell","year":"2020","journal-title":"Stud. Hist. Philos. Sci. Part B: Stud. Hist. Philos. Mod. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Wallace, D. (2012). The Emergent Multiverse: Quantum Theory According to the Everett Interpretation, Oxford University Press.","DOI":"10.1093\/acprof:oso\/9780199546961.001.0001"},{"key":"ref_22","unstructured":"Carroll, S. (2019). Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime, Dutton."},{"key":"ref_23","unstructured":"Bruce, C. (2004). Schr\u00f6dinger Rabbits: The Many Worlds of Quantum, The National Academic Press."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"166","DOI":"10.1103\/PhysRev.85.166","article-title":"A suggested interpretation of the quantum theory in terms of hidden variables-I and II","volume":"85","author":"Bohm","year":"1952","journal-title":"Phys. Rev."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Saunders, S., Barrett, J., Kent, A., and Wallace, D. (2010). Many Worlds? Everett, Quantum Theory, and Reality, Oxford University Press.","DOI":"10.1093\/acprof:oso\/9780199560561.001.0001"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"315","DOI":"10.1007\/s40509-015-0046-6","article-title":"Quantum mechanics as a deterministic theory of a continuum of worlds","volume":"2","year":"2015","journal-title":"Quantum Stud. Math. Found."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"266","DOI":"10.1086\/680190","article-title":"Quantum mechanics as classical physics","volume":"82","author":"Sebens","year":"2014","journal-title":"Philos. Sci."},{"key":"ref_28","first-page":"041013","article-title":"Quantum phenomena modeled by interactions between many classical worlds","volume":"4","author":"Hall","year":"2014","journal-title":"Phys. Rev. X"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1007\/s10701-022-00627-0","article-title":"Pilot-wave theory without nonlocality","volume":"52","author":"Tappenden","year":"2023","journal-title":"Found. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"424010","DOI":"10.1088\/1751-8113\/47\/42\/424010","article-title":"What Bell did","volume":"47","author":"Maudlin","year":"2014","journal-title":"J. Phys. A Math. Theor."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"424011","DOI":"10.1088\/1751-8113\/47\/42\/424011","article-title":"Comment on \u2018What Bell did\u2019","volume":"47","author":"Werner","year":"2014","journal-title":"J. Phys. A Math. Theor."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"424009","DOI":"10.1088\/1751-8113\/47\/42\/424009","article-title":"Quantum non-locality\u2014It ain\u2019t necessarily so","volume":"47","author":"Brukner","year":"2014","journal-title":"J. Phys. A Math. Theor."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1016\/j.shpsa.2022.11.008","article-title":"How and when did locality become \u2018local realism\u2019? A historical and critical analysis (1963\u20131978)","volume":"97","author":"Laudisa","year":"2023","journal-title":"Stud. Hist. Philos. Sci."},{"key":"ref_34","unstructured":"Drezet, A. (2023). Whence Nonlocality?. arXiv."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"3329","DOI":"10.1088\/0305-4470\/28\/12\/007","article-title":"A classical extension of quantum mechanics","volume":"8","author":"Beltrametti","year":"1995","journal-title":"J. Phys. A Math. Gen."},{"key":"ref_36","first-page":"14","article-title":"Should the wave-function be a part of the quantum ontological state?","volume":"4","author":"Drezet","year":"2012","journal-title":"Prog. Phys."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1007\/s10701-009-9347-0","article-title":"Einstein, incompleteness, an the epistemic view of quantum states","volume":"40","author":"Harrigan","year":"2010","journal-title":"Found. Phys."},{"key":"ref_38","unstructured":"Goldstein, S., Norsen, T., Tausk, D.V., and Zanghi, N. (2023, May 26). Scholarpedia: Bell\u2019s Theorem. Available online: http:\/\/www.scholarpedia.org\/article\/Bell%27s_theorem."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1261","DOI":"10.1119\/1.3630940","article-title":"Bell\u2019s Concept of Local Causality","volume":"79","author":"Norsen","year":"2011","journal-title":"Am. J. Phys."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1093\/bjps\/axp053","article-title":"Many-Worlds and Schr\u00f6dinger first quantum theory","volume":"62","author":"Allori","year":"2011","journal-title":"Br. J. Philos. Sci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1007\/BF00869434","article-title":"Interpreting the many-worlds interpretation","volume":"77","author":"Albert","year":"1988","journal-title":"Synthese"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1007","DOI":"10.1119\/1.3456564","article-title":"Bell\u2019s theorem and the causal arrow of time","volume":"78","author":"Argaman","year":"2010","journal-title":"Am. J. Phys."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"052115","DOI":"10.1103\/PhysRevA.86.052115","article-title":"All entangled states display some hidden nonlocality","volume":"86","author":"Liang","year":"2012","journal-title":"Phy. Rev. A"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Ben-Menahem, Y., and Hemmo, H. (2012). Probability in Physics, The Frontiers Collection, Springer. Chapter 18.","DOI":"10.1007\/978-3-642-21329-8"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1016\/j.shpsb.2018.10.003","article-title":"In defence of the self-location uncertainty account of probability in the many-worlds interpretation","volume":"66","author":"McQueen","year":"2019","journal-title":"Stud. Hist. Philos. Sci. Part B Stud. Hist. Philos. Mod. Phys."},{"key":"ref_46","unstructured":"Wallace, D. (2023, May 26). The Probability Puzzle and Many-Worlds Interpretation of Quantum Mechanics. Available online: https:\/\/www.youtube.com\/watch?v=AyMnfZ8cLII."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/j.shpsb.2017.02.001","article-title":"Typical Worlds","volume":"58","author":"Barrett","year":"2017","journal-title":"Stud. Hist. Philos. Mod. Phys."},{"key":"ref_48","unstructured":"Drezet, A. (2021). Collapse of the many-worlds interpretation: Why Everett\u2019s theory is typically wrong. arXiv."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Albert, Z.D. (2015). After Physics, Harvard University Press.","DOI":"10.4159\/harvard.9780674735507"},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Maudlin, T. (2019). Philosophy of Physics: Quantum Theory, Princeton University Press.","DOI":"10.1515\/9780691190679"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Hemmo, M., and Shenker, O. (2020). Quantum, Probability, Logic in Physics, Jerusalem Studies in Philosophy and History of Science, Springer Nature.","DOI":"10.1007\/978-3-030-34316-3"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"3129","DOI":"10.1098\/rspa.1999.0443","article-title":"Quantum theory of probability and decisions","volume":"456","author":"Deutsch","year":"1999","journal-title":"Proc. R. Soc. A"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"120404","DOI":"10.1103\/PhysRevLett.90.120404","article-title":"Environment-assisted invariance, entanglement, and probabilities in quantum physics","volume":"90","author":"Zurek","year":"2003","journal-title":"Phys. Rev. Lett."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"052105","DOI":"10.1103\/PhysRevA.71.052105","article-title":"Probabilities from entanglement, Born\u2019s rule pk=|\u03c8k|2 from envariance","volume":"71","author":"Zurek","year":"2005","journal-title":"Phys. Rev. A"},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"315","DOI":"10.1007\/s40509-021-00247-9","article-title":"Making sense of Born\u2019s rule p\u03b1=\u2225\u03a8\u03b1\u22252 with the many-minds interpretation","volume":"8","author":"Drezet","year":"2021","journal-title":"Quantum Stud. Math. Found."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"843","DOI":"10.1007\/BF01049004","article-title":"Quantum Equilibrium and the Origin of Absolute Uncertainty","volume":"67","author":"Goldstein","year":"1992","journal-title":"J. Stat. Phys."},{"key":"ref_57","doi-asserted-by":"crossref","unstructured":"Ghadimi, M., Hall, M.J.W., and Wiseman, H.M. (2018). Nonlocality in Bell\u2019s Theorem, in Bohm\u2019s Theory, and in Many Interacting Worlds Theorising. Entropy, 20.","DOI":"10.3390\/e20080567"},{"key":"ref_58","first-page":"67","article-title":"Analysis of Everett\u2019s quantum interpretation from the point of view of a Bohmian","volume":"2","author":"Drezet","year":"2016","journal-title":"Int. J. Quantum Found."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"521","DOI":"10.1007\/s13194-017-0198-9","article-title":"The wave-function as a multi-field","volume":"8","author":"Hubert","year":"2018","journal-title":"Euro. Jnl. Phil. Sci."},{"key":"ref_60","unstructured":"Bohm, D., and Hiley, B.J. (1993). The Undivided Universe, Routledge."},{"key":"ref_61","doi-asserted-by":"crossref","unstructured":"Bricmont, J. (2016). Making Sense of Quantum Mechanics, Springer. Chapter 5.","DOI":"10.1007\/978-3-319-25889-8"},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"1166","DOI":"10.1007\/s10701-019-00297-5","article-title":"Lorentz-invariant, retrocausal, and deterministic hidden variables","volume":"49","author":"Drezet","year":"2019","journal-title":"Found. Phys."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"080403","DOI":"10.1103\/PhysRevLett.121.080403","article-title":"Cosmic Bell test using random measurement settings from high-redshift quasars","volume":"121","author":"Rauch","year":"2018","journal-title":"Phys. Rev. Lett."},{"key":"ref_64","doi-asserted-by":"crossref","unstructured":"Knox, E., and Wilson, A. (2021). The Routledge Companion to the Philosophy of Physics, Routledge.","DOI":"10.4324\/9781315623818"}],"container-title":["Symmetry"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-8994\/15\/6\/1250\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:53:36Z","timestamp":1760126016000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-8994\/15\/6\/1250"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,6,12]]},"references-count":64,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2023,6]]}},"alternative-id":["sym15061250"],"URL":"https:\/\/doi.org\/10.3390\/sym15061250","relation":{},"ISSN":["2073-8994"],"issn-type":[{"type":"electronic","value":"2073-8994"}],"subject":[],"published":{"date-parts":[[2023,6,12]]}}}