# Initial Conditions ## Overview We use the multi-scale cosmological initial conditions creator `MUSIC`. `MUSIC` is a computer program to generate nested grid initial conditions for high-resolution “zoom” cosmological simulations. A detailed description of the algorithms can be found in Hahn & Abel (2011). You can download the user’s guide [here](https://bitbucket.org/ohahn/music/downloads/MUSIC_Users_Guide.pdf) or obtain a copy of the code [here](https://people.phys.ethz.ch/~hahn/MUSIC/). Any questions should be directed to [Brendan Griffen](mailto:brendan.f.griffen%40gmail.com) and then if that fails, [Oliver Hahn](mailto:hahn%40phys.ethz.ch). ## Parameters These are the parameter files which were used to generate the initial conditions for the *Caterpillar* project. We adopt the raw Planck (2013) cosmology and do not use 2nd order Lagrangian perturbation theory. The [user guide](https://bitbucket.org/ohahn/music/downloads/MUSIC_Users_Guide.pdf) contains all the information required to understand the following parameter files. Within each simulation directory, there is a file named `OUTPUTmusic` which gives the log of the construction of the initial conditions. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.caterpillarproject.org/technical/initial-conditions.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.