Speaker
Description
Light dark matter is usually constraint by large-scale structure observations via Lyman-$\alpha$ lines to $m_\text{DM}\gtrsim \mathcal{O}(5\text{keV})$. I will discuss how these bounds can be relaxed for dark sectors which are produced non-thermally from the SM bath but cool themselves via $2\leftrightarrow3$ "cannibal" reactions.
Thermodynamic predictions of this cooling are in many regions outweighed by the combined effect of dark sector depletion via decay to DM and simultaneous regeneration via inverse cannibal ($2\to3$) reactions.
In numerical studies, bounds are found to relax as low as 1keV even in simplistic SM extensions of only a cannibalizing scalar and a DM fermion. The cooling mechanism also works for dark sectors consisting of dark gauge bosons of a broken non-Abelian gauge symmetry SU(N), which naturally hosts cannibal reactions.
The models demonstrate a sizable relaxation of Lyman-$\alpha$ bounds, as well as the possibility to implement self-cooling mechanisms in wide-spread SM extensions without the need for uncommon ingredients.