News like today's new evidence for a standard model light* (~125 Gev) Higgs particle does much for theoretical physics. In one fell swoop many theories can be ruled out. While at the same time other theories gain direct support. Still other theories, and the theorist who propose them, are vindicated for putting their faith in the standard model. This model that has worked perfectly in every test it has had for 30 or so years. One area which this will affect in the latter way is that of quantum gravity.
Loop quantum gravity (LQG), casual dynamic triangulations (CDT), and group field theory (GFT) approaches and those who use them for the study of quantum gravity problems can smile a life affirmed smile today. The Higgs particle is that of the Standard Model without super symmetry. For a long time if one did not jump on the super symmetric bandwagon they were considered a crackpot by many. No more of that! For much more experimental detail on today's announcement see Tommaso Dorigo’s real time blog on the announcement from CERN.
If you are a person who has worked in this subfield you have dealt with the dominance of the super symmetric theories. The response to string theorist was "what if there is no super symmetry". Now we have good reason to make that question more than hypothetical. What was found today is very good evidence that non-standard Higgs particles which would indicate super symmetry don’t exist over a very wide range of energies. Finding the Higgs here, while not a test of those theories, certainly removes or weakens a common argument against them.
As one of those people who worked on the ideas of canonical quantum gravity this is sweet news indeed.
What does this mean for theoretical particle physics?
In short, there are a few kinds of models to watch out for.
- Models in which the standard model Higgs could be a composite of other particles bound together.
- Models in which a standard model Higgs is one of several Higgs's. A situation similar to the situation with the electron, muon and tauon or their neutrinos in a way.
- The door is still open for models in which there is no Higgs particle. Why? The statistical significance of today's results is such that further study could still show a mysterious bump, but never a true discovery.
It will take some time to fully digest just what today’s news means for quantum gravity beyond a strong support for the standard model. (Not to mention Peter Higgs getting a Nobel Prize). What this means for non-string, non-M-theory quantum gravity is that such theories deserved to be taken seriously. What this means for super symmetric theories that they can no longer hold the monopoly on the time of theorist.