Material accompanying the lecture 'Cosmological ICs and PT-informed integrators' by Oliver Hahn at Les Houches Summer School 2025 "The Dark Universe"

This lecture was part of the 2025 Les Houches Summer School "The Dark Universe"

You can access a recording of the full 90min lecture (along with all other lectures) as well as the lecture slides via indico

This repository contains

• the jupyter notebook used in the lecture, illustrating how to sample a Gaussian random field corresponding to a cosmic density field from a CAMB power spectrum, how to generate a displacement field for first order characteristics (Zel'dovich approximation), and how to render it in 3D using PyVista
• Lecture notes in PDF format, currently in draft form (notes are submitted but not yet peer reviewed)

The notebook is meant for educational purposes. To generate high-quality cosmological initial conditions for production simulations, consider using

• monofonIC for up to 3LPT ICs, incl. baryons, MPI-parallel, for single resolution precision cosmology simulations
• MUSIC for high-resolution zoom ICs up to 2LPT, with output for a huge range of codes