ETHOS - An Effective Theory of Structure Formation: Dark matter physics
  as a possible explanation of the small-scale CDM problems
  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 $2.8\times
10^4\,{\rm M}_\odot$ and a softening length of $72.4\,{\rm pc}$. 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.
