Title: Bouncing cosmology from nonlinear dark energy with two cosmological constants

Abstract: The Standard Model of Cosmology provides a successful framework for the history of our Universe, however there are problems which require addressing. A key problem is that singularities arise at high energies, and their current interpretation is that they represent points where General Relativity breaks down. These singularities arise assuming the strong energy conditions holds, however this energy condition is violated by dark energy. Therefore, it is worth considering non-singular bouncing cosmologies, which also require violation of the strong energy condition, as an alternate beginning of our Universe. In this talk, I will present the dynamics of standard matter and radiation with a nonlinear dark energy evolving between two cosmological constants. I will first discuss the sub-manifolds of the system, to show ΛCDM-like dynamics and highlight the behaviour of the dynamic dark energy which produces non-singular bounces. I will then present the full system to show the effect of including dark matter and radiation on the bounce, both when their energy densities can become infinite and when a maximum energy scale is enforced, such that these components appear at a certain energy scale. Finally, I will explain the caveats to these models, and discuss possible ways in which I can build on this work whilst avoiding these problems in future.