Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach

Perico, E. L. D.; Bernardini, Alex E.

doi:10.1088/1475-7516/2011/06/001

Cited by 2 publications

(2 citation statements)

References 28 publications

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“…Based on the code CLASS work [57], which we use for numerical integration, the free neutrino distribution function, f0 (q), is modeled here as warm dark matter, which is time independent. Other massive neutrino formulations in the literature include the Degenerate Fermion Gas approximation, see [58,59], while a timedependent distribution function was discussed by [60]. The collision term of the Boltzmann equation that reproduce the expression ( 25) is…”

Section: A Coupling Terms For Massive Neutrinosmentioning

confidence: 99%

Running vacuum cosmological models: linear scalar perturbations

Perico

Tamayo

2017

J. Cosmol. Astropart. Phys.

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In cosmology, phenomenologically motivated expressions for running vacuum are commonly parametrized as linear functions Λ(H 2 ) or Λ(R). Such kind of models assume an equation of state for vacuum given by P Λ = − ρ Λ , relating their background pressure P Λ and mean energy density ρ Λ ≡ Λ/8πG. This equation of state requires that the dynamic for vacuum is due to the energy exchange with the material species. Most of the approaches to background level consider only the energy exchange between vacuum and the transient dominant material component of the universe. We extend such models assuming the running vacuum as the sum of independent contributions ρ Λ = i ρ Λi , associated with (and interacting with) each of the i material species. We derive the linear scalar perturbations for two running scenarios, modeling its cosmic evolution and identifying their different imprints on the cosmic microwave background anisotropies and the matter power spectrum. In the Λ(H 2 ) scenario the running vacuum are coupled with all the material species in the universe, whereas the Λ(R) description only leads to coupling between vacuum and the non-relativistic matter components; which produces different imprints of the two models on the matter power spectrum. A comparison with the Planck 2015 data was made in order to constrain the free parameters of the models. In the case of the Λ(H 2 ) model, it was found that Ω Λ = 0.705 ± 0.027 and H 0 = 69.6 ± 2.9 km M pc −1 s −1 , which diminish the tension with the low redshift expectations. * elduartep@usp.br †

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Section: A Coupling Terms For Massive Neutrinosmentioning

confidence: 99%

Running vacuum cosmological models: linear scalar perturbations

Perico

Tamayo

2017

J. Cosmol. Astropart. Phys.

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“…equation (23) from reference [7]) the density matrix describes a coherent collection of spinorial particles that exhibit spin and parity as correlated quantum features, through which a suitable interference phenomena between parity doublets is identified. Furthermore, setting = q p T the Fermi-Dirac distribution can be written as [7][8][9][10]…”

Section: Correlation Between the Intrinsic Degrees Of Freedommentioning

confidence: 99%

Relativistic dynamics compels a thermalized fermi gas to a unique intrinsic parity eigenstate

Bernardini¹,

Mizrahi²

2014

Phys. Scr.

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Dirac equation describes the dynamics of a relativistic spin-1/2 particle regarding its spatial motion and intrinsic degrees of freedom. Here we adopt the point of view that the spinors describe the state of a massive particle carrying two qubits of information: helicity and intrinsic parity.We show that the density matrix for a gas of free fermions, in thermal equilibrium, correlates helicity and intrinsic parity. Our results introduce the basic elements for discussing the spin-parity correlation for a Fermi gas: (1) at the ultra-relativistic domains, when the temperature is quite high, T > 10 10 K, the fermions have no definite intrinsic parity (50% : 50%), which is maximally correlated with the helicity; (2) at very low temperature, T ≈ 3 K, a unique parity dominates (conventionally chosen positive), by 10 20 to 1, while the helicity goes into a mixed state for spin up and down, and the quantum correlation decoheres. For the anti-fermions we get the opposite behavior. In the framework of quantum information, our result could be considered as a plausible explanation of why we do accept, as a fact (consistent with the experimental observation), that fermions (and anti-fermions), in our present epoch of a cool universe, have a unique intrinsic parity.The framework for constructing spin-parity entangled states is established.

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Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach

Cited by 2 publications

References 28 publications

Running vacuum cosmological models: linear scalar perturbations

Running vacuum cosmological models: linear scalar perturbations

Relativistic dynamics compels a thermalized fermi gas to a unique intrinsic parity eigenstate

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