Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity
Over the last decade, it has been found that nonlinear laws of composition of momenta are predicted by some alternative approaches to “real” 4D quantum gravity, and by all formulations of dimensionally-reduced (3D) quantum gravity coupled to matter. The possible relevance for rather different quantu...
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| Format: | Article |
| Language: | English |
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MDPI AG
2017-08-01
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| Series: | Entropy |
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| Online Access: | https://www.mdpi.com/1099-4300/19/8/400 |
| _version_ | 1811263094125494272 |
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| author | Giovanni Amelino-Camelia |
| author_facet | Giovanni Amelino-Camelia |
| author_sort | Giovanni Amelino-Camelia |
| collection | DOAJ |
| description | Over the last decade, it has been found that nonlinear laws of composition of momenta are predicted by some alternative approaches to “real” 4D quantum gravity, and by all formulations of dimensionally-reduced (3D) quantum gravity coupled to matter. The possible relevance for rather different quantum-gravity models has motivated several studies, but this interest is being tempered by concerns that a nonlinear law of addition of momenta might inevitably produce a pathological description of the total momentum of a macroscopic body. I here show that such concerns are unjustified, finding that they are rooted in failure to appreciate the differences between two roles for laws composition of momentum in physics. Previous results relied exclusively on the role of a law of momentum composition in the description of spacetime locality. However, the notion of total momentum of a multi-particle system is not a manifestation of locality, but rather reflects translational invariance. By working within an illustrative example of quantum spacetime, I show explicitly that spacetime locality is indeed reflected in a nonlinear law of composition of momenta, but translational invariance still results in an undeformed linear law of addition of momenta building up the total momentum of a multi-particle system. |
| first_indexed | 2024-04-12T19:38:27Z |
| format | Article |
| id | doaj.art-524ab8b70c6a437fb6c00d7c231ed3e8 |
| institution | Directory Open Access Journal |
| issn | 1099-4300 |
| language | English |
| last_indexed | 2024-04-12T19:38:27Z |
| publishDate | 2017-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Entropy |
| spelling | doaj.art-524ab8b70c6a437fb6c00d7c231ed3e82022-12-22T03:19:09ZengMDPI AGEntropy1099-43002017-08-0119840010.3390/e19080400e19080400Planck-Scale Soccer-Ball Problem: A Case of Mistaken IdentityGiovanni Amelino-Camelia0Dipartimento di Fisica, Università di Roma “La Sapienza”, P.le A. Moro 2, 00185 Roma, ItalyOver the last decade, it has been found that nonlinear laws of composition of momenta are predicted by some alternative approaches to “real” 4D quantum gravity, and by all formulations of dimensionally-reduced (3D) quantum gravity coupled to matter. The possible relevance for rather different quantum-gravity models has motivated several studies, but this interest is being tempered by concerns that a nonlinear law of addition of momenta might inevitably produce a pathological description of the total momentum of a macroscopic body. I here show that such concerns are unjustified, finding that they are rooted in failure to appreciate the differences between two roles for laws composition of momentum in physics. Previous results relied exclusively on the role of a law of momentum composition in the description of spacetime locality. However, the notion of total momentum of a multi-particle system is not a manifestation of locality, but rather reflects translational invariance. By working within an illustrative example of quantum spacetime, I show explicitly that spacetime locality is indeed reflected in a nonlinear law of composition of momenta, but translational invariance still results in an undeformed linear law of addition of momenta building up the total momentum of a multi-particle system.https://www.mdpi.com/1099-4300/19/8/400quantum foundationsrelativityquantum gravity |
| spellingShingle | Giovanni Amelino-Camelia Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity Entropy quantum foundations relativity quantum gravity |
| title | Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity |
| title_full | Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity |
| title_fullStr | Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity |
| title_full_unstemmed | Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity |
| title_short | Planck-Scale Soccer-Ball Problem: A Case of Mistaken Identity |
| title_sort | planck scale soccer ball problem a case of mistaken identity |
| topic | quantum foundations relativity quantum gravity |
| url | https://www.mdpi.com/1099-4300/19/8/400 |
| work_keys_str_mv | AT giovanniamelinocamelia planckscalesoccerballproblemacaseofmistakenidentity |