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The fluid of primordial fluctuations. (English) Zbl 0932.83051

Summary: We formulate a phenomenological model where the inflaton fluctuations are treated as a fluid. By applying the hydrodynamic equations to this fluid we recover the conventional result that relates the spectrum of density fluctuations in the inflaton field at reentering the horizon to the spectrum of fluctuations at the time a scale leaves the horizon. Moreover, through the equivalent viscosity of the fluid we obtain a Reynolds number that suggests turbulent motion, which implies that mode-mode coupling in the inflaton field cannot be neglected. For de Sitter inflation the resulting spectrum using turbulence theory is scale invariant on all scales of interest. This suggests that the hypothesis of an extremely weakly coupled inflation could be relaxed without affecting the predictions of the model.

MSC:

83F05 Relativistic cosmology
80A10 Classical and relativistic thermodynamics
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