What are the shortcomings of the standard model?
- In the standard model as it comes, the pattern of groups, representations, and (especially) hypercharges is a patchwork.
- In the standard model as it comes a great discovery of recent years the existence of small non-zero neutrino masses, appears gratuitous. One can accommodate those masses using non-renormalizable, mass dimension 5 operators, but even then the fact that masses of neutrinos are far far smaller than masses of their charged lepton cousins lacks context.
- In the standard model as it comes there is no evident link between the standard model and the remaining major force of Nature, i.e. gravity. - That is, GR is not here? (my comment)
- In the standard model as it comes there is no evident accounting for the bulk of the mass in the universe, i.e. the dark matter and dark energy.
- In the standard model as it comes there is no explanation for the empirical smallness of the P and T violating angle (phi) term.
- Masses and mixing angles among quarks and leptons are not constrained by any deep principles, and this sector of the standard model brings in a plethora of unworthy “fundamental” constants.
- The triplication of families is gratuitous. -The fourth generation?
- The gauge principle translates mathematical symmetry into physical law.
- The observed interaction symmetries and fermion representations fit into a larger, unifying symmetry and unifying representation very economically.
- Gauge symmetry can be spontaneously broken.
- Coupling constants evolve with distance, or energy.
2010) PoS EPS-Hep 2009, hep-ph1003.4672