Pions of a dark sector gauge group can be strongly interacting massive particle (SIMP) matter, produced by the freeze-out $3 \to 2$ interactions, with naturally large self-interactions. We study if adding photon to set-up do it all: i) maintain thermalization visible sector, ii) resonantly enhance $3\to2$ thus allowing for perturbative pion description, and iii) provide velocity dependent self-...

This paper concerns (but does not succeed in performing) the diffeomorphism classification of closed, oriented, differential, simply-connected 4-manifolds. It arises out of the observation (due to Pontrjagin and Milnor [2]) that if two such manifolds Mx and M2 have isomorphic quadratic forms of intersection numbers on #2(Jft-), then there is a map / : M1-^-Mi which is a homotopy equivalence and...