A strongly interacting massive particle (SIMP) is a hypothetical particle that interacts strongly between themselves and weakly with ordinary matter, but could form the inferred dark matter despite this.
[1][2][3] Strongly interacting massive particles have been proposed as a solution for the ultra-high-energy cosmic-ray problem[4][5] and the absence of cooling flows in galactic clusters.
[6][7] Various experiments and observations have set constraints on SIMP dark matter from 1990 onward.
[11][citation needed] Measurements of Uranus's heat excess exclude SIMPs from 150 MeV to 104 GeV.
[14] Earth's heat flow significantly constrains any cross section.