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Can the clustered dark matter and the smooth dark energy arise from the same scalar field ?

T. Padmanabhan·T. Roy Choudhury
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Abstract

Cosmological observations suggest the existence of two different kinds of energy densities dominating at small ($ \lesssim 500$ Mpc) and large ($\gtrsim 1000 $ Mpc) scales. The dark matter component, which dominates at small scales, contributes $Ω_m \approx 0.35$ and has an equation of state $p=0$ while the dark energy component, which dominates at large scales, contributes $Ω_V \approx 0.65$ and has an equation of state $p\simeq -ρ$. It is usual to postulate wimps for the first component and some form of scalar field or cosmological constant for the second component. We explore the possibility of a scalar field with a Lagrangian $L =- V(ϕ) \sqrt{1 - \del^i ϕ\del_i ϕ}$ acting as {\it both} clustered dark matter and smoother dark energy and having a scale dependent equation of state. This model predicts a relation between the ratio $ r = ρ_V/ρ_{\rm DM}$ of the energy densities of the two dark components and expansion rate $n$ of the universe (with $a(t) \propto t^n$) in the form $n = (2/3) (1+r) $. For $r \approx 2$, we get $n \approx 2$ which is consistent with observations.

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T. Padmanabhan, T. Roy Choudhury. 2002-11-06. Can the clustered dark matter and the smooth dark energy arise from the same scalar field ?. https://doi.org/10.1103/physrevd.66.081301

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