Dark Matter Equation of State through Cosmic History

Kopp, Michael; Skordis, Constantinos; Thomas, Daniel B.; Ilić, Stéphane

doi:10.1103/physrevlett.120.221102

Cited by 55 publications

(45 citation statements)

References 57 publications

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“…The value of w is negative because˜ c > c andh > h. This negative value indicates that dark matter is not formed by particles, for which w must lie between 0 (nonrelativistic limit) and 1/3 (ultrarelativistic limit) [31]. This value agrees with the results of [30], which analyzed the dark matter equation of state between z = 10 5 and z = 0 using the CMB and BAO data. Those results showed that w is consistent with 0 but allows a small negative value.…”

supporting

confidence: 82%

“…We use the cosmological constant as dark energy because it can naturally arise from the simplest Lagrangian for the gravitational field in which the torsion tensor is the only variable [29]. We show that dark matter satisfying an equation of state p = w [30], where p is the pressure and is the energy density, with w ≈ −0.01 instead of w = 0 removes the discrepancy.…”

mentioning

confidence: 99%

“…Therefore, if dark matter has a generalized equation of state [30,36,37] with a negative parameter w, such a parameter has no fluid-mechanical interpretation; it only represents how dark matter interacts gravitationally and influences the dynamics of the universe. Accordingly, dark matter (without additional generalizations) cannot be a dark fluid composed of particles and its non-particle nature should be investigated.…”

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confidence: 99%

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Non-particle dark matter from Hubble parameter

Popławski

2019

Eur. Phys. J. C

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The measurements of the Hubble parameter using the cosmic microwave background radiation appear to be inconsistent with the measurements of this parameter using Cepheid variable stars. This inconsistency may be a result of using the CDM cosmology, which assumes pressureless dark matter, in extrapolating the data from the recombination time to the present time. We show that both measurements are consistent if dark matter satisfies an equation of state in which the pressure p and the energy density are related by p = w with a negative value of w. The data give w ≈ −0.01. The negative value of w indicates that dark matter would not be formed by particles, which is consistent with the lack of experimental evidence for them.The observations of the temperature angular power spectrum of the cosmic microwave background (CMB) radiation provide the information about the composition of the universe [1]. The measurements of the position of the first acoustic peak show that the universe is nearly flat, with the density parameter ≈ 1. The measurements of the amplitudes of the peaks determine the values of b h 2 and c h 2 , where b is the density parameter for baryonic matter, c is the density parameter for dark matter, and the present-day Hubble parameter H 0 = 100h km/s/Mpc. Combining these values with the measured h = 0.674 ± 0.005 gives (omitting errors) b = 0.049 and c = 0.265, as obtained by the Planck satellite [2,3]. Consequently, the density parameter for total matter is m = 0.314.Before the Planck measurements, most measured values of h also clustered around 0.68, including the data from high-redshift type Ia supernovae (SN Ia) [4,5], Wilkinson Microwave Anisotropy Probe CMB data [6], baryon acoustic oscillations (BAO) [7], SN Ia and BAO data [8], measurements of the Hubble parameter at intermediate redshifts [9], and large-scale-structure data [10]. Assuming a flat universe, = 1 − m = 0.686 for dark energy (cosmological constant). The resulting age of the universe is t univ = a e-mail: NPoplawski@newhaven.edu da/(a H) =

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confidence: 82%

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confidence: 99%

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confidence: 99%

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Non-particle dark matter from Hubble parameter

Popławski

2019

Eur. Phys. J. C

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“…Note that the original GDM description also accounted for negative pressure and a nonvanishing viscosity c 2 vis;gdm . The effects of this modeling on the expansion and linear perturbations have been recently studied in [21][22][23][24][25][26]. Here we decided not to include the contribution of the viscosity c 2 vis;gdm since at the linear level it is degenerate with the sound speed c 2 s;gdm .…”

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confidence: 99%

Spherical collapse in generalized dark matter models

2020

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The influence of considering a generalized dark matter (GDM) model, which allows for a non-pressureless dark matter and a nonvanishing sound speed in the nonlinear spherical collapse model is discussed for the Einstein-de Sitter-like and ΛGDM models. By assuming that the vacuum component responsible for the accelerated expansion of the Universe is not clustering and therefore behaving similarly to the cosmological constant Λ, we show how the change in the GDM characteristic parameters affects the linear density threshold for collapse of the nonrelativistic component (δ c ) and its virial overdensity (Δ V ). We found that a positive GDM equation of state parameter, w gdm , is responsible for lower values of δ c as compared to the standard spherical collapse model and that this effect is much stronger than the one induced by a change in the GDM sound speed, c 2 s;gdm . We also found that Δ V is only slightly affected and mostly sensitive to w gdm . These effects could be relatively enhanced for lower values of the matter density. We found that the effects of the additional physics on δ c and Δ V , when translated to nonlinear observables such as the halo mass function, induce an overall deviation of about 40% with respect to the standard ΛCDM model at late times for high mass objects. However, within the current constraints for c 2 s;gdm and w gdm , we found that these changes are the consequence of properly taking into account the correct linear matter power spectrum for the GDM model while the effects coming from modifications in the spherical collapse model remain negligible. Using a phenomenologically motivated approach, we also study the nonlinear matter power spectrum and found that the additional properties of the dark matter component lead, in general, to a strong suppression of the nonlinear power spectrum with respect to the corresponding ΛCDM one. Finally, as a practical example, we compare ΛGDM and ΛCDM using galaxy cluster abundance measurements, and found that these small scale probes will allow us to put more stringent constraints on the nature of dark matter.

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“…1, the equation of state parameter changes with the redshift and hence is time dependent. It turns out that the above problem of time dependent equation of state parameter is equivalent to that of an interacting dark energy fluid, which has been extensively studied in [28][29][30][31][32][33][34][35][36][37]. Using Monte Carlo Markov Chain technique one can demonstrate that models involving interacting dark energy (or, time dependent equation of state parameter) has degeneracy between the matter density and the dark energy interaction rate.…”

mentioning

confidence: 99%

Late-time acceleration driven by shift-symmetric Galileon in the presence of torsion

Banerjee

Chakraborty

Mukherjee³

2018

Phys. Rev. D

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A shift-symmetric Galileon model in presence of spacetime torsion has been constructed for the first time. This has been realized by localizing (or, gauging) the Galileon symmetry in flat spacetime in an appropriate manner. We have applied the above model to study the evolution of the universe at a cosmological scale. Interestingly, for a wide class of torsional structures we have shown that the model leads to late time cosmic acceleration. Furthermore, as torsion vanishes, our model reproduces the standard results.

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Dark Matter Equation of State through Cosmic History

Cited by 55 publications

References 57 publications

Non-particle dark matter from Hubble parameter

Non-particle dark matter from Hubble parameter

Spherical collapse in generalized dark matter models

Late-time acceleration driven by shift-symmetric Galileon in the presence of torsion

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