SÉMINAIRE DU GRECO
"Generation of vorticity in our universe: a perturbative approach" |
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Giulia Cusin |
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We compute the generation of vorticity from velocity dispersion in the dark matter fluid. If dark matter is described as a perfect fluid at zero temperature, Helmholtz’s theorem dictates that no vorticity is generated. We go beyond this standard description and we allow the dark matter fluid to have a non-vanishing velocity dispersion. This implies a modification to the usual hydrodynamical system (continuity & Euler equations): the Boltzmann hierarchy has to be considered up to the second moment. As a consequence, the Euler equation is modified with a source term that describes the effect of non-zero velocity dispersion. We write an equation for the Eulerian vorticity in Lagrangian coordinates and show that it has a growing mode already at second order in perturbation theory. We compute the power spectrum of the vorticity and of the rotational component of velocity at second order in perturbation theory. |
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lundi 13 février 2017 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
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