Geometric Perfect Fluids and Dark Side of the Universe
| Autor: | Gürses, Metin, Heydarzade, Yaghoub, Şentürk, Çetin |
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| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Phys. Rev. D 110, 024073 (2024) |
| Druh dokumentu: | Working Paper |
| Popis: | Recently we showed that in FLRW cosmology, the contribution from higher curvature terms in any generic metric gravity theory to the energy-momentum tensor is of the perfect fluid form. Such a geometric perfect fluid can be interpreted as a fluid remaining from the beginning of the universe where the string theory is thought to be effective. Just a short time after the beginning of the Universe, it is known that the Einstein-Hilbert action is assumed to be modified by adding all possible curvature invariants. We propose that the observed late-time accelerating expansion of the Universe can be solely driven by this geometric fluid. To support our claim, we specifically study the quadratic gravity field equations in $D$-dimensions. We show that the field equations of this theory for the FLRW metric possess a geometric perfect fluid source containing two critical parameters $\sigma_1$ and $\sigma_2$. To analyze this theory concerning its parameter space $(\sigma_1, \sigma_2)$, we obtain the general second-order nonlinear differential equation governing the late-time dynamics of the deceleration parameter $q$. Hence using some present-day cosmological data as our initial conditions, our findings for the $\sigma_2=0$ case are as follows: $ (i)$ In order to have a positive energy density for the geometric fluid $\rho_g$, the parameter $\sigma_1$ must be negative for all dimensions up to $D = 11$, $(ii)$ For a suitable choice of $\sigma_1$, the deceleration parameter experiences signature changes in the past and future, and in the meantime it lies within a negative range which means that the current observed accelerated expansion phase of the Universe can be driven solely by the curvature of the spacetime, $(iii)$ $q$ experiences a signature change and as the dimension $D$ of spacetime increases, this signature change happens at earlier and later times, in the past and future, respectively. Comment: 27 pages, 4 figures, published version |
| Databáze: | arXiv |
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