The Variation of <i>G</i> and Λ in Cosmology
The idea of varying constants of nature is very old, and has commanded a lot of attention since first mooted. The variation in the gravitational parameter <i>G</i> and cosmological parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="...
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| Format: | Article |
| Language: | English |
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MDPI AG
2024-10-01
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| Series: | Universe |
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| Online Access: | https://www.mdpi.com/2218-1997/10/11/404 |
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| Summary: | The idea of varying constants of nature is very old, and has commanded a lot of attention since first mooted. The variation in the gravitational parameter <i>G</i> and cosmological parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> is still an active area of research. Since the idea of a varying <i>G</i> was introduced by Dirac almost a century ago, there are even theories that have variable <i>G</i> such as the Brans–Dicke theory and the scale covariant theory. Both these theories also have a varying <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> in their full generalisations. A varying <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> was also introduced around the same time as that of varying <i>G</i>. It is interesting to note that a possible solution to the cosmological constant problem can be realised from a dynamic <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula>. In this work, we focus on a varying <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> and <i>G</i> framework. In almost all studies in the simplest framework of variables <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> and <i>G</i>, it is found that one of them has to increase with time. However, observations and theoretical considerations indicate that both <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> and <i>G</i> should decrease with time. In this paper, we propose a solution to this problem, finding theories in which both <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mo>Λ</mo></semantics></math></inline-formula> and <i>G</i> decrease with time. |
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| ISSN: | 2218-1997 |