Impacts of Viscous Matter and Radiation on the Temporal Evolution of the Universe
Keywords:classical general relativity, classical statistical mechanics, early Universe
We propose that the cosmic background is simply characterized by an equation of state of a relativistic fluid consisting of homogeneously and isotropically distributed single particle and single photon. Other components such as dark matter and dark energy (cosmological constant) are not taken into consideration. We assume that the expansion of the Universe is isotropic. Accordingly, the shear viscosity coefficient vanishes. We have derived expressions for the energy density and the bulk viscosity and found that both quantities largely increase with the inclusion of the photon. As for their temporal evolution, there is a rapid decrease in the early stages of the Universe. This seems to saturate at large co-moving time. We also found that the scale factor in non-viscous and viscous cosmic backgrounds is almost non-distinguishable in the early Universe. The latter suggest going beyond the standard cosmological model (SCM). The nonviscous cosmic background seems to have a scale factor larger than that of the viscous one. The result obtained for the temporal evolution of the Hubble parameter confirms the scale factor results. Namely, the distinguishability between non-viscous and viscous cosmic backgrounds is the largest in the early Universe.
A. Tawfik, M. Wahba, H. Mansour, T. Harko. Viscous quark-gluon plasma in the early universe. Annalen Phys. 523, 194 (2011).
A. Tawfik, T. Harko, H. Mansour, M. Wahba. Dissipative processes in the early universe: Bulk viscosity. Uzbek J. Phys. 12, 316 (2010).
A. Tawfik. Cosmological consequences of QCD phase transition(s) in early universe. AIP Conf. Proc. 1115 (1), 239 (2009).
A. Tawfik. Thermodynamics in the viscous early universe. Can. J. Phys. 88, 825 (2010).
A. Tawfik, H. Magdy. Thermodynamics of viscous matter and radiation in the early universe. Can. J. Phys. 90, 433 (2012).
I. Newton. Principia (Macmillian and Co., 1863).
Atsushi Nakamura, Sunao Sakai. Transport coefficients of gluon plasma. Phys. Rev. Lett. 94, 072305 (2005).
S. Sakai, A. Nakamura. Transport coefficient of gluon plasma from lattice QCD. PoS LAT2005, 186 (2006).
A. Nakamura, S. Sakai. Viscosities of hot gluon: A lattice QCD study. Nucl. Phys. A 774, 775 (2006).
A.N. Tawfik, C. Greiner. Bulk viscosity in strong and electroweak matter. Int. J. Mod. Phys. E 30 (08), 2150067 (2021).
A.N. Tawfik, C. Greiner. Early Uuiverse thermodynamics and evolution in nonviscous and viscous strong and electroweak epochs: Possible analytical solutions. Entropy 23 (3), 295 (2021).
M. Gyulassy, L. McLerran. New forms of QCD matter discovered at RHIC. Nucl. Phys. A 750, 30 (2005).
D. Kharzeev, K. Tuchin. Bulk viscosity of QCD matter near the critical temperature. JHEP 9, 093 (2008).
F. Karsch, D. Kharzeev, K. Tuchin. Universal properties of bulk viscosity near the QCD phase transition. Phys. Lett. B 663, 217 (2008).
A.N. Tawfik, I. Mishustin. Equation of state for cosmological matter at and beyond QCD and electroweak eras. J. Phys. G 46 (12), 125201 (2019).
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