Unimodular Approaches to the Cosmological Constant Problem
We review selected aspects of unimodular gravity and we discuss its viability as a solution of the old cosmological constant problem. In unimodular gravity, the cosmological constant is promoted to a global degree of freedom. We highlight the importance of correctly setting up its initial data in or...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-03-01
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| Series: | Universe |
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| Online Access: | https://www.mdpi.com/2218-1997/9/3/131 |
| _version_ | 1797608745925083136 |
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| author | Pavel Jiroušek |
| author_facet | Pavel Jiroušek |
| author_sort | Pavel Jiroušek |
| collection | DOAJ |
| description | We review selected aspects of unimodular gravity and we discuss its viability as a solution of the old cosmological constant problem. In unimodular gravity, the cosmological constant is promoted to a global degree of freedom. We highlight the importance of correctly setting up its initial data in order to achieve a resolution of the cosmological constant problem on a semi-classical level. We review recent path integral analysis of quantum aspects of unimodular gravity to note that the semi-classical findings carry over to the quantum level as well. We point out that a resolution of the problem inherently relies on a global constraint on the spacetime four-volume. This makes the theory closely related to the vacuum energy sequester, which operates in a similar way. We discuss possible avenues of extending unimodular gravity that preserve the resolution of the cosmological constant problem. |
| first_indexed | 2024-03-11T05:47:49Z |
| format | Article |
| id | doaj.art-1bcbebe8c0964f6b95bfba967aa9e511 |
| institution | Directory Open Access Journal |
| issn | 2218-1997 |
| language | English |
| last_indexed | 2024-03-11T05:47:49Z |
| publishDate | 2023-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Universe |
| spelling | doaj.art-1bcbebe8c0964f6b95bfba967aa9e5112023-11-17T14:15:53ZengMDPI AGUniverse2218-19972023-03-019313110.3390/universe9030131Unimodular Approaches to the Cosmological Constant ProblemPavel Jiroušek0High Energy Physics, Cosmology & Astrophysics Theory Group, University of Cape Town, Private Bag, Cape Town 7700, South AfricaWe review selected aspects of unimodular gravity and we discuss its viability as a solution of the old cosmological constant problem. In unimodular gravity, the cosmological constant is promoted to a global degree of freedom. We highlight the importance of correctly setting up its initial data in order to achieve a resolution of the cosmological constant problem on a semi-classical level. We review recent path integral analysis of quantum aspects of unimodular gravity to note that the semi-classical findings carry over to the quantum level as well. We point out that a resolution of the problem inherently relies on a global constraint on the spacetime four-volume. This makes the theory closely related to the vacuum energy sequester, which operates in a similar way. We discuss possible avenues of extending unimodular gravity that preserve the resolution of the cosmological constant problem.https://www.mdpi.com/2218-1997/9/3/131unimodular gravitycosmological constant problemmodified gravityWeyl invariance |
| spellingShingle | Pavel Jiroušek Unimodular Approaches to the Cosmological Constant Problem Universe unimodular gravity cosmological constant problem modified gravity Weyl invariance |
| title | Unimodular Approaches to the Cosmological Constant Problem |
| title_full | Unimodular Approaches to the Cosmological Constant Problem |
| title_fullStr | Unimodular Approaches to the Cosmological Constant Problem |
| title_full_unstemmed | Unimodular Approaches to the Cosmological Constant Problem |
| title_short | Unimodular Approaches to the Cosmological Constant Problem |
| title_sort | unimodular approaches to the cosmological constant problem |
| topic | unimodular gravity cosmological constant problem modified gravity Weyl invariance |
| url | https://www.mdpi.com/2218-1997/9/3/131 |
| work_keys_str_mv | AT paveljirousek unimodularapproachestothecosmologicalconstantproblem |