Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND
General relativity and its Newtonian weak field limit are not sufficient to explain the observed phenomenology in the Universe, from the formation of large-scale structures to the dynamics of galaxies, with the only presence of baryonic matter. The most investigated cosmological model, the <inlin...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-01-01
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| Series: | Universe |
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| Online Access: | https://www.mdpi.com/2218-1997/9/1/56 |
| _version_ | 1797436645521227776 |
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| author | Valentina Cesare |
| author_facet | Valentina Cesare |
| author_sort | Valentina Cesare |
| collection | DOAJ |
| description | General relativity and its Newtonian weak field limit are not sufficient to explain the observed phenomenology in the Universe, from the formation of large-scale structures to the dynamics of galaxies, with the only presence of baryonic matter. The most investigated cosmological model, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>CDM, accounts for the majority of observations by introducing two dark components, dark energy and dark matter, which represent ∼95% of the mass-energy budget of the Universe. Nevertheless, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>CDM model faces important challenges on the scale of galaxies. For example, some very tight relations between the properties of dark and baryonic matters in disk galaxies, such as the baryonic Tully–Fisher relation (BTFR), the mass discrepancy–acceleration relation (MDAR), and the radial acceleration relation (RAR), which see the emergence of the acceleration scale <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>a</mi><mn>0</mn></msub><mo>≃</mo><mn>1.2</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></mrow></semantics></math></inline-formula> m s<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></semantics></math></inline-formula>, cannot be intuitively explained by the CDM paradigm, where cosmic structures form through a stochastic merging process. An even more outstanding coincidence is due to the fact that the acceleration scale <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>a</mi><mn>0</mn></msub></semantics></math></inline-formula>, emerging from galaxy dynamics, also seems to be related to the cosmological constant <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>. Another challenge is provided by dwarf galaxies, which are darker than what is expected in their innermost regions. These pieces of evidence can be more naturally explained, or sometimes even predicted, by modified theories of gravity, that do not introduce any dark fluid. I illustrate possible solutions to these problems with the modified theory of gravity MOND, which departs from Newtonian gravity for accelerations smaller than <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>a</mi><mn>0</mn></msub></semantics></math></inline-formula>, and with Refracted Gravity, a novel classical theory of gravity introduced in 2016, where the modification of the law of gravity is instead regulated by a density scale. |
| first_indexed | 2024-03-09T11:05:37Z |
| format | Article |
| id | doaj.art-e5f4df43ce1248ee93ba6baf76899ff0 |
| institution | Directory Open Access Journal |
| issn | 2218-1997 |
| language | English |
| last_indexed | 2024-03-09T11:05:37Z |
| publishDate | 2023-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Universe |
| spelling | doaj.art-e5f4df43ce1248ee93ba6baf76899ff02023-12-01T00:59:36ZengMDPI AGUniverse2218-19972023-01-01915610.3390/universe9010056Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MONDValentina Cesare0National Institute for Astrophysics, Astrophysical Observatory of Catania, Via Santa Sofia 78, 95123 Catania, CT, ItalyGeneral relativity and its Newtonian weak field limit are not sufficient to explain the observed phenomenology in the Universe, from the formation of large-scale structures to the dynamics of galaxies, with the only presence of baryonic matter. The most investigated cosmological model, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>CDM, accounts for the majority of observations by introducing two dark components, dark energy and dark matter, which represent ∼95% of the mass-energy budget of the Universe. Nevertheless, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>CDM model faces important challenges on the scale of galaxies. For example, some very tight relations between the properties of dark and baryonic matters in disk galaxies, such as the baryonic Tully–Fisher relation (BTFR), the mass discrepancy–acceleration relation (MDAR), and the radial acceleration relation (RAR), which see the emergence of the acceleration scale <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>a</mi><mn>0</mn></msub><mo>≃</mo><mn>1.2</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></mrow></semantics></math></inline-formula> m s<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></semantics></math></inline-formula>, cannot be intuitively explained by the CDM paradigm, where cosmic structures form through a stochastic merging process. An even more outstanding coincidence is due to the fact that the acceleration scale <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>a</mi><mn>0</mn></msub></semantics></math></inline-formula>, emerging from galaxy dynamics, also seems to be related to the cosmological constant <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>. Another challenge is provided by dwarf galaxies, which are darker than what is expected in their innermost regions. These pieces of evidence can be more naturally explained, or sometimes even predicted, by modified theories of gravity, that do not introduce any dark fluid. I illustrate possible solutions to these problems with the modified theory of gravity MOND, which departs from Newtonian gravity for accelerations smaller than <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>a</mi><mn>0</mn></msub></semantics></math></inline-formula>, and with Refracted Gravity, a novel classical theory of gravity introduced in 2016, where the modification of the law of gravity is instead regulated by a density scale.https://www.mdpi.com/2218-1997/9/1/56modified gravitydark mattergalaxy dynamicsacceleration scalescaling relationsLSB galaxies |
| spellingShingle | Valentina Cesare Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND Universe modified gravity dark matter galaxy dynamics acceleration scale scaling relations LSB galaxies |
| title | Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND |
| title_full | Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND |
| title_fullStr | Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND |
| title_full_unstemmed | Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND |
| title_short | Dark Coincidences: Small-Scale Solutions with Refracted Gravity and MOND |
| title_sort | dark coincidences small scale solutions with refracted gravity and mond |
| topic | modified gravity dark matter galaxy dynamics acceleration scale scaling relations LSB galaxies |
| url | https://www.mdpi.com/2218-1997/9/1/56 |
| work_keys_str_mv | AT valentinacesare darkcoincidencessmallscalesolutionswithrefractedgravityandmond |