The Cosmic coincidence in Brans-Dicke cosmologies
May, 2005Citations per year
Abstract: (arXiv)
Among the suggested solutions to the cosmological constant problem, we find the idea of a dynamic vacuum, with an energy density decaying with the universe expansion. We investigate the possibility of a variation in the gravitational constant as well, induced, at the cosmological scale, by the vacuum decay. We consider an effective Brans-Dicke theory in the spatially flat FLRW spacetime, finding late time solutions characterized by a constant ratio between the matter and vacuum energy densities. By using the observed limits for the universe age, we fix the only free parameter of our solutions, obtaining a relative matter density in the range 0.25-0.4. In particular, for Ht = 1 we obtain a relative matter density equals to 1/3. This constitutes a possible explanation for another problem related to the cosmological term, the cosmic coincidence problem.Note:
- This essay received an honorable mention in the 2005 Essay Competition of the Gravity Research Foundation
- Cosmological constant
- scalar-tensor theories
- Brans-Dicke model
- energy: density
- energy: decay
- cosmological constant
- gravitation: fundamental constant
- fundamental constant: time dependence
- matter: density
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