Speaker
Quentin Vigneron
(CRAL, ENSL, Université Lyon 1)
Description
In Inhomogeneous Cosmology, restricting attention to an irrotational dust matter model, backreaction arises in terms of the deviation of the averaged spatial scalar curvature from a constant-curvature model, $\mathcal{W_D}$, and the kinematical backreaction, $\mathcal{Q_D}$. The resulting cosmological equations can be written in Friedmannian form featuring an effective scalar field in place of the backreaction, called the morphon field. A simple example for this morphon field is the class of scaling solutions where $\mathcal{W_D}$ and $\mathcal{Q_D}$ are assumed to follow a power law of the volume scale factor $a_\mathcal{D}$. The corresponding exact solutions can describe models of effective quintessence, arising with the morphon, but these and other models still assume the existence of dark matter in addition to the known sources. The contribution from backreaction, however, can change its sign to mimic dark matter-like effects. We here investigate the correspondence between the morphon field and fundamental scalar field dark matter models, in order to describe cosmological dark matter as an effective phenomenon arising from kinematical backreaction and the averaged spatial curvature of the inhomogeneous Universe. We further investigate the inverse problem by starting from exact scaling solutions and approximate solutions for structure formation and determine the properties of the corresponding morphon field.
