Abstract
Recent observations indicate that the Universe is expanding at an accelerated rate. This acceleration is commonly described by a component called dark energy. However, the exact nature of dark energy is unknown and is perhaps one of the biggest mysteries in cosmology today. Alternatives to dark energy require some form of modification to general relativity, and are often dubbed modified gravity. We consider gravity models that couples a scalar field with matter, which gives rise to an additional gravitational force called the fifth force. Local gravity constraints shows that the strength of the fifth force is very small. However, this could be due to a “screening mechanism” that hides the fifth force in high density environments. Two types of screening mechanism are considered in this thesis: the symmetron and chameleon screening. The halos, and more recently the voids, of the cosmic web are a common probe of modified gravity theories. The cosmic filaments, on the other hand, are less studied. In this thesis, we look for possible probes of modified gravity theories on the filaments of the cosmic web. We use DisPerSE, which utilizes discrete Morse Theory, on the dark matter particles, simulated by the N-body code ISIS/RAMSES, to identify the filaments of the cosmic web at z = 0. We present how modified gravity change the global properties of the filaments which includes their masses, lengths and thicknesses. We will also analyse the different speed components and density profiles of the filaments. Generally, we find that the properties are strongly affected by the presence of the fifth force, making the cosmic filaments a good probe of modified gravity.
Veileder: Professor David F. Mota, Institutt for teoretisk astrofysikk, UiO
Medveiledere: Postdoctoral researcher Bridget Falck & Postdoctoral researcher Max Grönke, UC Santa Barbara, USA
Intern sensor: Førsteamanuensis, Boris Vilhelm Gudiksen, Institutt for teoretisk astrofysikk, UiO
Ekstern sensor: Postdoctoral researcher, Hans Arnold Winther, University of Portsmouth