Bonn 2020 – scientific programme

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GR: Fachverband Gravitation und Relativitätstheorie

GR 12: Cosmology

GR 12.2: Talk

Thursday, April 2, 2020, 14:15–14:30, H-HS IV

Cosmological structure formation beyond the perfect fluid approximation — •Alaric Erschfeld — Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 16, D-69120 Heidelberg, Germany

Late time cosmological structure formation is often studied in a perfect pressureless fluid approximation in which dark matter is described in terms of its mass density and velocity. Deviations from a homogeneous and isotropic background cosmology are treated perturbatively, leading to good agreement with observations and simulations on large scales. On smaller scales on the other hand the perfect pressureless fluid approximation breaks down due to the phenomenon of shell-crossing. Further, standard cosmological perturbation theory is not applicable anymore since the deviations from the background cosmology become highly non-linear.

In order to overcome the limitations of the perfect pressureless fluid approximation, we extend the description of dark matter in a kinetic theory approach, taking the velocity dispersion tensor into account. To tackle the regime where the deviations are non-linear, we employ the Martin-Siggia-Rose/Janssen-De Dominicis formalism describing dark matter in terms of a statistical field theory. This allows to use resummation techniques such as the one-particle irreducible scheme as well as study the functional renormalisation group for cosmological structure formation.