Dark matter modelling:
We have developed and implemented a hybrid phase-space tessellation/N-body scheme that is able to combine the advantages of tessellation methods (Hahn+2013, Hahn&Angulo 2016) to provide a continuous density field in lower density regions, with the advantages of N-body methods in regions of rapid phase mixing in high density regions (see Figure 1)
We have conducted a thorough study of the premature disruption of subhaloes in N-body simulations and developed a library of idealised simulations of subhalo disruption that can serve as a foundation to develop physical models for the survival rates of subhaloes/satellites in cold dark matter haloes such as our Milky. The simulation data together with a non-parametric machine learned model is available through this website:
https://cosmo.oca.eu/dash(odnośnik otworzy się w nowym oknie)Large-scale structure dynamics: We have studied the dynamics of large-scale structure and measured, to our knowledge for the first time using N-body simulations the anisotropic stress that arises after anisotropic shell-crossing in multi-stream regions of the evolving dark matter fluid. All these results have been published in various papers.
We have published (in collaboration with Raul Angulo) a (gold open access) scientific review article on large-scale dark matter simulations summarising the state-of-the-art of the field along with pedagogical material on all relevant backgrounds.
Initial conditions:
We have developed a web-based database and interface called “cosmICweb” to explore numerical Universes, select objects for re-simulations and provide unique identifiers to objects. This already allows to e.g. easily select a set of Milky Way like object at high redshift, and resimulate it with a simulation code of your choice, and then pass on the ‘ID’ of that object (e.g. in a publication) for other researchers to study and simulate the same object. The database is already functional, we are currently integrating also the dataset from the Eagle simulation (Schaye et al.) and will release it publicly for beta-testing in the coming months. See attached Figure 2a/b. The development version is hosted at
https://cosmics-dev.oca.eu(odnośnik otworzy się w nowym oknie)We have begun the overhaul of the MUSIC initial conditions generator. This will be done in two steps: The first step will be a single resolution version of MUSIC 2.0 that includes higher order perturbation theory (including nLPT recursion, accurate treatment of CDM-baryon 2-fluid ICs, primordial non-Gaussianity, and arbitrary homogeneous background cosmologies) and directly integrates the CLASS code. It has been publicly released and is continuously updated. Development on the Zoom-version has begun but was not finished at the time of the end of the project.
Regarding initial conditions for baryons in Eulerian (grid) codes, we have made major progress through the development of semiclassical techniques that practically allow to perform Lagrangian perturbation theory for a Eulerian field (cf. Uhlemann et al. 2019). This can dramatically increase the accuracy of baryon initial conditions for codes like RAMSES, ART or ENZO.
Several papers relating to various aspects of the generation of initial conditions, higher accuracy perturbation theory, etc. have been published in scientific journals.
We have developed the cosmICweb database, which is publicly available and which allows to browse existing simulations (including the EAGLE simulation) to select objects for zoom resimulations. A paper discussing its features is about to be submitted.
Baryon modelling:
We have studied the impact of anisotropic thermal conduction at variance with AGN feedback on cosmological hydrodynamical simulations of galaxy cluster formation and evolution with a particular focus on cosmological observables and scaling relations from clusters. A paper summarising all results has been submitted and is expected to be published soon.
