Interaction between matter and radiation at very high temperatures: I. Compton scattering

Herrera, María; Hacyan, Shahen

doi:10.1063/1.865323

Cited by 8 publications

(3 citation statements)

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“…The functions D 1 and D 3 are symmetric with respect to permutations of any variables and D 2 is symmetric under permutations 1 ↔ 2 and 3 ↔ 4. In what follows we present the expression for D 2 (3,4). Without loss of generality we can assume that q 1 > q 2 and q 3 > q 4 .…”

Section: A Reduction Of the Collision Integralmentioning

confidence: 99%

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Non-equilibrium corrections to the spectra of massless neutrinos in the early universe

Dolgov¹,

Hansen²,

1997

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We repeat our previous calculation of the spectrum distortion of massless neutrinos in the early universe with a considerably better accuracy and corrected for a missing numerical factor in one of the two ways of calculations presented in our paper [1]. Now both ways of calculations are in perfect agreement and we essentially reproduce our old results presented in the abstract of the paper and used in the calculations of light element abundances. We disagree with the criticism of our calculations presented in ref.[2].

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Section: A Reduction Of the Collision Integralmentioning

confidence: 99%

“…The overall neutrino heating under assumption of equilibrium spectra has been considered earlier in refs. [2,3,4]. In this approximation the problem is very much simplified but the method itself is far from being precise from the very beginning.…”

Section: Introductionmentioning

confidence: 99%

Non-equilibrium corrections to the spectra of massless neutrinos in the early universe

Dolgov¹,

Hansen²,

1997

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“…Our simple model is based on a one-component fluid. In [14], relaxation time processes are incorporated in a two-fluid model. In this setting, electrons and positrons on the one side and neutrinos and antineutrinos on the other side, are found to be in two different equilibrium states with slightly different temperatures.…”

Section: Introductionmentioning

confidence: 99%

Backreaction Effects of Dissipation in Neutrino Decoupling

Maartens

Triginer

2000

General Relativity and Gravitation

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Dissipative effects during neutrino decoupling in the early universe create a small backreaction on the Hubble rate, and lead to a small rise in temperature and entropy. We use a simplified thermohydrodynamic model, which provides a causal approximation to kinetic theory, in order to estimate the backreaction effects and the entropy production. I. INTRODUCTIONNon-equilibrium processes in the early universe are typically associated with dynamical transitions or particle decouplings. In the case of neutrino decoupling, the standard approach is to treat the process as adiabatic (see e.g.[1]). The small non-equilibrium effects are thus usually neglected, which provides a reasonable approximation. However, given the increasing accuracy of cosmological observations and theoretical modeling, it is worthwhile revisiting the standard equilibrium models of processes such as neutrino decoupling, in order to see whether non-equilibrium corrections can lead to observable consequences. Recently, non-equilibrium corrections in neutrino decoupling have been calculated in a number of papers, using complicated kinetic theory and numerical computations (see [2] for a short review). The corrections are very small, as expected. For example, in [3][4][5] it was found that non-equilibrium effects lead to a small change in the decoupling temperature for neutrinos. Spectral distortions have also been analyzed [6], showing the remarkable fact that they amount to as much as 1% or more for the higher-energy side of the spectrum. Although these corrections in the spectrum, energy density and temperature of the neutrino component have hardly any effect on primordial helium synthesis, yielding a change in the mass fraction of ∼ 10 −4 , they can lead to other effects that may be observable. Thus it is shown that the non-equilibrium increase in neutrino temperature, which leads to an extra injection of energy into the photon spectrum, leads to a shift of equilibrium epoch between matter and radiation which, in turn, modifies the angular spectrum of fluctuations of the cosmic microwave background radiation [7,8].Despite the accuracy of these models in obtaining corrections to the decoupling temperature and distribution function due to non-equilibrium effects, they still make use of the standard Friedman equations for a perfect (i.e nondissipative) fluid. This leads to the physically inconsistent situation in which, say, the energy density and expansion evolve in time like a radiative fluid in equilibrium. One expects that small distortions in the particle equilibrium distribution function should be reflected in the macroscopic (i.e fluid) description, as given by the stress-energy tensor, by adding a bulk viscous pressure to the equilibrium one. Here we consider an alternative thermo-hydrodynamic model of dissipative effects in neutrino decoupling, simple enough to produce analytic solutions for the backreaction effects on the universal scale factor, and estimates for the entropy production due to dissipation. As explained above these effects are...

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Neutrinos in cosmology

2002

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Cosmological implications of neutrinos are reviewed. The following subjects are discussed at a different level of scrutiny: cosmological limits on neutrino mass, neutrinos and primordial nucleosynthesis, cosmological constraints on unstable neutrinos, lepton asymmetry of the universe, impact of neutrinos on cosmic microwave radiation, neutrinos and the large scale structure of the universe, neutrino oscillations in the early universe, baryo/lepto-genesis and neutrinos, neutrinos and high energy cosmic rays, and briefly some more exotic subjects: neutrino balls, mirror neutrinos, and neutrinos from large extra dimensions. Content

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Interaction between matter and radiation at very high temperatures: I. Compton scattering

Cited by 8 publications

References 8 publications

Non-equilibrium corrections to the spectra of massless neutrinos in the early universe

Non-equilibrium corrections to the spectra of massless neutrinos in the early universe

Backreaction Effects of Dissipation in Neutrino Decoupling

Neutrinos in cosmology

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