Cosmological simulations of dark scattering and baryon scattering models

The most-widely accepted cosmological model \(\Lambda\) Cold Dark Matter (\lcdm) predicts a flat Universe with baryonic matter, dark matter, and radiation making up about \(30\%\) of the total energy budget, while dark energy (DE) constitutes the remaining \(70\%\). DE is a mysterious component responsible for the Universe's late-time accelerated expansion. Despite its successes, the \lcdm model has several issues and open questions, prompting the exploration of alternative DE theories. This thesis focuses on a specific class of coupled DE models where DE interacts with matter through a Thomson-like elastic scattering, involving pure momentum exchange. These models have been studied using N-body simulations, primarily analyzing scattering between DE and a single matter component, revealing significant non-linear effects. We used the N-body code \texttt{GADGET-4}, together with the \texttt{PANDA} module, to conduct a suite of cosmological simulations to extend the current understanding of these interactions. In the first part of this work, we incorporated adiabatic hydrodynamics of baryons and a phenomenological screening mechanism in DE-baryon scattering models. Our findings indicate that hydrodynamics efficiently screens the interaction between DE and baryons compared to our defined screening mechanism. In the second part, we combined multiple scattering with a time-varying DE equation of state to identify models capable of producing a non-linear suppression of the power spectrum, potentially addressing the \(S_8\) tension. However, these models require further refinement, including the integration of baryonic physics, to achieve the desired suppression. This research is the first of its kind, potentially paving the way for new investigations into the interplay between DE and matter.