Quintessence: an analytical study, with theoretical and observational applications
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arXiv
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2024
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| _version_ | 1866909620568588288 |
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| author | Andriot, David |
| author_facet | Andriot, David |
| contents | We focus on minimally coupled (multi)field quintessence models, of thawing type, and their realistic solutions. In a model-independent manner, we describe analytically these cosmological solutions throughout the universe history. Starting with a kination - radiation domination phase, we obtain an upper bound on the scalar potential to guarantee an early kination: $V(φ) \ll e^{-\sqrt{6} φ}$. Turning to the radiation - matter phase, we obtain analytic expressions for the scale factor $a(t)$ (not $t(a)$) and the scalar fields $φ^i(t)$ (usually neglected). These allow us to evaluate analytically the freezing of scalar fields, typically $Δφ\lesssim 10^{-2}$, as well as the transition moment of the dark energy equation of state parameter $w_φ$ from $+1$ to $-1$, with excellent agreement to the numerics. We comment on this freezing in view of string theory model building, and of some cosmological events. Turning to the latest phase of matter - dark energy domination, we show that the (multi)field displacement is sub-Planckian: $Δφ\leq 1$. We also provide for that phase analytic expressions for $\int (w_φ+1)\, d N$ in terms of matter evolution; we relate those to observational targets that we propose. Using finally the CPL parametrisation, while discussing a phantom behaviour, we derive analytic bounds on $w_0$ and $w_a$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_17182 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Quintessence: an analytical study, with theoretical and observational applications Andriot, David High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology We focus on minimally coupled (multi)field quintessence models, of thawing type, and their realistic solutions. In a model-independent manner, we describe analytically these cosmological solutions throughout the universe history. Starting with a kination - radiation domination phase, we obtain an upper bound on the scalar potential to guarantee an early kination: $V(φ) \ll e^{-\sqrt{6} φ}$. Turning to the radiation - matter phase, we obtain analytic expressions for the scale factor $a(t)$ (not $t(a)$) and the scalar fields $φ^i(t)$ (usually neglected). These allow us to evaluate analytically the freezing of scalar fields, typically $Δφ\lesssim 10^{-2}$, as well as the transition moment of the dark energy equation of state parameter $w_φ$ from $+1$ to $-1$, with excellent agreement to the numerics. We comment on this freezing in view of string theory model building, and of some cosmological events. Turning to the latest phase of matter - dark energy domination, we show that the (multi)field displacement is sub-Planckian: $Δφ\leq 1$. We also provide for that phase analytic expressions for $\int (w_φ+1)\, d N$ in terms of matter evolution; we relate those to observational targets that we propose. Using finally the CPL parametrisation, while discussing a phantom behaviour, we derive analytic bounds on $w_0$ and $w_a$. |
| title | Quintessence: an analytical study, with theoretical and observational applications |
| topic | High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2410.17182 |