ETHOS – an effective theory of structure formation: dark matter physics as a possible explanation of the small-scale CDM problems

Abstract

We present the first simulations within an effective theory of structure formation (ETHOS), which includes the effect of interactions between dark matter and dark radiation on the linear initial power spectrum and dark matter self-interactions during non-linear structure formation. We simulate a Milky Way-like halo in four different dark matter models and the cold dark matter case. Our highest resolution simulation has a particle mass of 2.8 × 10 4 M and a softening length of 72.4 pc. We demonstrate that all alternative models have only a negligible impact on large scale structure formation. On galactic scales, however, the models significantly affect the structure and abundance of subhaloes due to the combined effects of small scale primordial damping in the power spectrum and late time self-interactions. We derive an analytic mapping from the primordial damping scale in the power spectrum to the cutoff scale in the halo mass function and the kinetic decoupling temperature. We demonstrate that certain models within this extended effective framework that can alleviate the too-big-to-fail and missing satellite problems simultaneously, and possibly the core-cusp problem. The primordial power spectrum cutoff of our models naturally creates a diversity in the circular velocity profiles, which is larger than that found for cold dark matter simulations. We show that the parameter space of models can be constrained by contrasting model predictions to astrophysical observations. For example, some models may be challenged by the missing satellite problem if baryonic processes were to be included and even over-solve the too-big-to-fail problem; thus ruling them out.

Matter power spectrum in hidden neutrino interacting dark matter models: a closer look at the collision term

“…Interacting DM effectively reduces the abundance of substructures in a galactic halo to a similar degree to that some WDM models do [27][28][29][30][31][32][33][34][35][36].…”

Small-Scale Challenges to the ΛCDM Paradigm

“…Such models produce results that are a hybrid between traditional WDM and SIDM with scale-invariant spectra (e.g. Vogelsberger et al 2016). Specifically, it is possible to modify dark matter in such a way that it produces both fewer subhalos (owing to power spectra effects) and constant density cores (owing to particle self-interactions) and thus solve the substructure problem and core/cusp problem simultaneously without appealing to strong baryonic feedback.…”

Make dark matter charged again

“…[40][41][42][43][44][45][46][47][48]), but can also in principle impose serious constraints. This model, which we shall refer to here as darkly-charged dark matter, is simple from a particle physics perspective but leads to extremely interesting consequences in astrophysics.…”