Theories of dark energy

Abstract

Dark energy has been believed to be responsible for the universe's accelerated expansion. Since its discovery in 1998 through the observation of type 1a supernovae, it is found to constitute 68% of the universe's energy density. Different models have been brought forward over the last three decades to explain the origin and nature of dark energy. However, no single accepted model can still explain all the phenomena observed. Most models for dark energy can be divided into two categories: Modified matter models and modified gravity models. Both arise from modifications to both sides of Einstein's field equations. In this report, the first part will cover the observational proof for dark energy. The second part will explore different models and cover some of their fundamental principles. Finally, this report will discuss higher dimensional theories, which postulate that higher dimensional space is responsible for the weakening of gravity in our universe, which is what we perceive as cosmic acceleration.