Understanding the reason behind the observed accelerating expansion of the Universe is one of the most notable puzzles in modern cosmology, and conceivably in fundamental physics. In the upcoming years, near future surveys will probe structure formation with unprecedented precision and will put firm constraints on the cosmological parameters, including those that describe properties of dark energy. In light of this, in the first part of my talk, I'm going to show a systematic extension of the Effective Field Theory of Dark Energy framework to non-linear clustering. As a first step, we have studied the k-essence model and have developed a relativistic N-body code, k-evolution.
I'm going to talk about the k-evolution results, including the effect of k-essence perturbations on the matter and gravitational potential power spectra and the k-essence structures formed around the dark matter halos. In the second part of my talk, I'm going to show that for some choice of parameters the k-essence non-linearities suffer from a new instability and blow up in finite time.
This talk is based on: arXiv:2204.13098, arXiv:2205.01055, arXiv:2107.14215, arXiv:2007.04968, arXiv:1910.01105, arXiv:1910.01104.
Zoom Link: https://pitp.zoom.us/j/99797451101?pwd=dituM2d2MDFCbDgyVXJ4c2s1NVoyUT09