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1975
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Robert Simon, « Density fluctuations in an expanding viscous and conducting universe (II) », Bulletins de l'Académie Royale de Belgique (documents), ID : 10.3406/barb.1975.57976
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. — The effect of radiative viscosity and thermal conductivity on density fluctuations in a hot Einstein-de Sitter expanding universe is investigated, in the frame of general relativity, in the radiative period before decoupling, by means of the Thomas expression for the stress-energy tensor. Initial conditions are taken as general and density fluctuations evolve according to a superposition of two acoustic modes and one conductive mode. When irreversible effects become important, in the course of the expansion, the two acoustic modes are exponentially damped, but the conductive mode remains remarkably stationary. Numerical integrations have been realized for masses ranging between 1020 and 108 solar masses, between R = 10-2 (R = 1 corresponds to equipartition of energy between matter and radiation) and R = 18.2 (decoupling).
