# Remarks on Cosmological Bulk Viscosity in Different Epochs

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Possible Relationship to the Bulk Viscosity in the Lepton-Photon Epoch

## 3. Discussion

#### Comparison with the Result ${\zeta}_{\mathrm{D}}\sim {\rho}^{-0.4}$ Obtained by Yang et al.

## 4. The Viscous Kasner Universe

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

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**Table 1.**The table should be read horizontally and shows the numerical values of $\zeta $ calculated by Equation (8) for different parameter value inputs $\{\lambda ,{\zeta}_{0},{\mathsf{\Omega}}_{0}\}$. The parameter values given in the three first columns are used as input when calculating the values for $\zeta $ in the rightmost column.

Table Showing $\mathit{\zeta}$ Estimates | ||||||
---|---|---|---|---|---|---|

$\lambda $$(-)$ | ${\zeta}_{0}$$(\mathrm{Pa}\phantom{\rule{0.166667em}{0ex}}\mathrm{s})$ | ${\mathsf{\Omega}}_{0}$ | $\zeta $ from Equation (8) $(\mathrm{Pa}\phantom{\rule{0.166667em}{0ex}}\mathrm{s})$ | |||

0 | $\forall \phantom{\rule{0.166667em}{0ex}}{\zeta}_{0}$ | (0,1] | $\zeta \phantom{\rule{0.166667em}{0ex}}=\phantom{\rule{0.166667em}{0ex}}{\zeta}_{0}$ | |||

$1/2$ | ${\zeta}_{0}={10}^{4}$ | [0.1,1] | ∼${10}^{21}$ | |||

$1/2$ | ${\zeta}_{0}={10}^{5}$ | [0.1,1] | ∼${10}^{22}$ | |||

$1/2$ | ${\zeta}_{0}={10}^{6}$ | [0.1,1] | ∼${10}^{23}$ | |||

1 | ${\zeta}_{0}={10}^{4}$ | [0.9,1] | ∼${10}^{38}$ | |||

1 | ${\zeta}_{0}={10}^{5}$ | [0.9,1] | ∼${10}^{39}$ | |||

1 | ${\zeta}_{0}={10}^{6}$ | [0.9,1] | ∼${10}^{40}$ |

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Brevik, I.; Normann, B.D.
Remarks on Cosmological Bulk Viscosity in Different Epochs. *Symmetry* **2020**, *12*, 1085.
https://doi.org/10.3390/sym12071085

**AMA Style**

Brevik I, Normann BD.
Remarks on Cosmological Bulk Viscosity in Different Epochs. *Symmetry*. 2020; 12(7):1085.
https://doi.org/10.3390/sym12071085

**Chicago/Turabian Style**

Brevik, Iver, and Ben David Normann.
2020. "Remarks on Cosmological Bulk Viscosity in Different Epochs" *Symmetry* 12, no. 7: 1085.
https://doi.org/10.3390/sym12071085