  Self-interacting dark matter (SIDM) offers the potential to mitigate some of
the discrepancies between simulated cold dark matter (CDM) and observed
galactic properties. We introduce a physically motivated SIDM model to
understand the effects of self interactions on the properties of Milky Way and
dwarf galaxy sized haloes. This model consists of dark matter with a nearly
degenerate excited state, which allows for both elastic and inelastic
scattering. In particular, the model includes a significant probability for
particles to up-scatter from the ground state to the excited state. We simulate
a suite of zoom-in Milky Way-sized N-body haloes with six models with different
scattering cross sections to study the effects of up-scattering in SIDM models.
We find that the up-scattering reaction greatly increases the central densities
of the main halo through the loss of kinetic energy. However, the physical
model still results in significant coring due to the presence of elastic
scattering and down-scattering. These effects are not as apparent in the
subhalo population compared to the main halo, but the number of subhaloes is
reduced compared to CDM.
