Particle physics minimalism for the 2010s

Physics today has a standard idea of what lies beyond the standard model - supersymmetry, grand unification, string theory - and such models tend to be very complicated. But occasionally someone constructs what I call a neo-minimalist theory of everything - adding the bare minimum to the standard model that is required to incorporate new data from cosmology, astrophysics, and neutrino physics.

To my mind, the two leading neo-minimal models are the "new minimal standard model" (NMSM) and the "neutrino minimal standard model" (nuMSM). To the standard model, the NMSM adds two right-handed neutrinos and two scalars (an inflaton and a dark matter particle). The nuMSM just adds three right-handed neutrinos, and proposes to use the Higgs as the inflaton.

There is essentially just one paper about the NMSM, but it describes how the NMSM addresses all the data. The nuMSM is elaborated across many papers.

It's probably time that new minimal models were made, in the light of new data. The observed Higgs is just below the range of allowed masses in the NMSM (when considered as a theory valid all the way to the Planck scale), while the nuMSM managed to predict the Higgs mass, on the hypothesis of special boundary conditions at that scale. We now have a variety of possible dark-matter signals, though none of them are confirmed. (I find it intriguing that CDMS-II may be seeing something of mass O(10 GeV), like one of the unstable heavy neutrinos in the nuMSM.) We have new cosmological constraints on inflation and on the composition of the universe.

Both NMSM and nuMSM explain dark energy via a cosmological constant. I think minimalism should also consider quintessence - dark energy from a new scalar field.