Dubbed SMASH, the model is based on the standard model of particle physics, but has a few bits tacked on. The standard model is a collection of particles and forces that describes the building blocks of the universe. Although it has passed every test thrown at it, it can’t explain some phenomena.
They extend the Standard Model with a new complex singlet scalar field σ and two Weyl fermions Q and Q˜ in the 3 and ¯3 representations of SU(3)c and with charges −1/3 and 1/3 under U(1)Y .
The origin of the baryon asymmetry of the Universe is explained in SMASH from thermal leptogenesis. This requires massive RH neutrinos acquiring equilibrium abundances and then decaying when production rates become Boltzmann suppressed.
Arxiv - Unifying inflation with the axion, dark matter, baryogenesis and the seesaw mechanism
A minimal extension of the Standard Model (SM) providing a complete and consistent picture of particle physics and cosmology up to the Planck scale is presented. We add to the SM three right-handed SM-singlet neutrinos, a new vector-like color triplet fermion and a complex SM singlet scalar σ whose vacuum expectation value at ∼ 10^11 GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously. Primordial inflation is produced by a combination of σ and the SM Higgs. Baryogenesis proceeds via thermal leptogenesis. At low energies, the model reduces to the SM, augmented by seesaw-generated neutrino masses, plus the axion, which solves the strong CP problem and accounts for the dark matter in the Universe. The model can be probed decisively by the next generation of cosmic microwave background and axion dark matter experiments.
SOURCES - Arxiv