{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T21:47:13Z","timestamp":1788472033538,"version":"build-2803163510"},"reference-count":44,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2024,2,10]],"date-time":"2024-02-10T00:00:00Z","timestamp":1707523200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100006209","name":"U.S. Department of Energy, Office of Science, Office of Nuclear Physics","doi-asserted-by":"publisher","award":["DE-AC05-00OR22725"],"award-info":[{"award-number":["DE-AC05-00OR22725"]}],"id":[{"id":"10.13039\/100006209","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>A semantic adjustment to what physicists mean by the terms \u2018special relativity\u2019 and \u2018general relativity\u2019 is suggested, which prompts a conceptual shift to a more unified perspective on physics governed by the Poincar\u00e9 group and physics governed by the Galilei group. After exploring the limits of a unified perspective available in the setting of 4-dimensional spacetime, a particular central extension of the Poincar\u00e9 group\u2014analogous to the Bargmann group that is a central extension of the Galilei group\u2014is presented that deepens a unified perspective on Poincar\u00e9 and Galilei physics in a 5-dimensional spacetime setting. The immediate focus of this paper is classical physics on affine 4-dimensional and 5-dimensional spacetimes (\u2018special relativity\u2019 as redefined here), including the electrodynamics that gave rise to Poincar\u00e9 physics in the first place, but the results here may suggest the existence of a \u2018Galilei general relativity\u2019 more extensive than generally known, to be pursued in the sequel.<\/jats:p>","DOI":"10.3390\/sym16020214","type":"journal-article","created":{"date-parts":[[2024,2,12]],"date-time":"2024-02-12T03:50:27Z","timestamp":1707709827000},"page":"214","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A Unified Perspective on Poincar\u00e9 and Galilei Relativity: I. Special Relativity"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0086-105X","authenticated-orcid":false,"given":"Christian Y.","family":"Cardall","sequence":"first","affiliation":[{"name":"Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6354, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,2,10]]},"reference":[{"key":"ref_1","unstructured":"Penrose, R. (2004). The Road to Reality: A Complete Guide to the Laws of the Universe, Jonathan Cape."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Gourgoulhon, E. (2013). Special Relativity in General Frames, Springer. 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