Instabilités gravitationnelles de champs de Yang-Mills et de champs scalaires dans l'univers primordial

Abstract

The gravitational instability of Yang-Mills fields is studied by means of a numerical integration of the hamiltonian formulation of Einstein-Yang-Mills equations, which describe the coupling between gravitation and a gauge field. A two-step evolution appears to rule this mechanism: the fluctuations first dilute, as a sequel of the conformal invariance of the gauge theory; then, the fluctuations undergo oscillations of increasing amplitude as the solution moves away from the homogeneous one. An interesting comparison with the gravitational instability of a scalar field has also been made. Finally, we have established that the quintessence scalar fields inhibit the formation of dark matter halos. By analysing the results of a modified N-body code, we show that those fields produce less structures and lighter halos, and lead to significative differences that allow to distinguish either a quintessence scenario from a more conventional one with a cosmological constant either different quintessence models.

Date of Award	2004
Original language	French
Awarding Institution	University of Namur
Supervisor	Anne Lemaitre (Co-Supervisor), Dominique Lambert (Co-Supervisor), Philippe Lambin (Jury), Alain MOUSSIAUX (Jury), Jean-Michel Alimi (Jury) & M. VOLKOV (Jury)