A geometrical approach to nonlinear perturbations in relativistic cosmology

David Langlois (1) , Filippo Vernizzi (1, 2)

1 UPD7 - Université Paris Diderot - Paris 7
2 CEA

We give a pedagogical review of a covariant and fully non-perturbative approach to study nonlinear perturbations in cosmology. In the first part, devoted to cosmological fluids, we define a nonlinear extension of the uniform-density curvature perturbation and derive its evolution equation. In the second part, we focus our attention on multiple scalar fields and present a nonlinear description in terms of adiabatic and entropy perturbations. In both cases, we show how the formalism presented here enables one to easily obtain equations up to second, third and higher orders.

Mots clés: Physical Sciences

David Langlois, Filippo Vernizzi. A geometrical approach to nonlinear perturbations in relativistic cosmology. Classical and Quantum Gravity, 2010, 27 (12), pp.124007. ⟨10.1088/0264-9381/27/12/124007⟩. ⟨hal-00601893⟩