DYNAMICS OF DARK MATTER AND DARK ENERGY UNIFICATION USING SCALAR FIELDS WITH NON-CANONICAL LAGRANGIANS

• Main Author: Suhendra, Alvin
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85563
• Institution: Institut Teknologi Bandung

Many theoretical models have been proposed to explain dark matter and dark energy. However, so far, there is no strong experimental evidence supporting the existence of either. The simplest model of dark energy, namely the cosmological constant ?, still faces issues known as the fine-tuning problem and the cosmic coincidence problem. Therefore, and considering the unexplored aspects of physics in the dark sector, several proposals have been put forward, one of which involves a unification approach, including the use of a single scalar field in a non-canonical Lagrangian. In this thesis research, the author investigates the evolution of the scalar field, tests its stability using autonomous equations, and analyzes the perturbations arising due to the presence of this scalar field. The scalar field behaves like cold dark matter when its kinetic term is much larger than its potential term, and like dark energy when the opposite is true. There are four critical points in the autonomous system, which correlate with the radiation-dominated universe, baryons, the kinetic term, and the potential term. The critical point at the potential term is stable, making it an attractor point. This is consistent with cosmological observations indicating that the universe is currently undergoing accelerated expansion. Perturbation analysis is conducted to observe matter perturbations and the growth of large-scale structures. The growth rate of structures increases slowly until z ? 2, indicating that structures can grow without the presence of CDM.