The virtue of so-called Higgs inflation models is that they might explain inflation within the current Standard Model of particle physics, which successfully describes how most known particles and forces behave. Interest in the Higgs is running hot this summer because CERN, the lab in Geneva, Switzerland, that runs the LHC, has said it will announce highly anticipated findings regarding the particle in early July.
The problem with many of these models is that when they are run, the Higgs decreases in energy too quickly and therefore would not generate fluctuations seen in the cosmic microwave background radiation. As such, they require the existence of additional fields to accomplish all the effects of inflation, ruining the simplicity one would desire from such models in the first place.
A Higgs inflation model that Shaposhnikov and colleague Fedor Bezrukov at the University of Connecticut proposed in 2007 (pdf) eliminated the need for such extra fields by suggesting the Higgs interacts with gravity in a different way than other particles. This would allow the Higgs to keep its energy long enough to result in the kind of universe we see today. Mazumdar says the difficulty this idea faces is why the Higgs would have this special relationship with gravity to begin with when no other particle does, or why it would interact very weakly as proposed.
Instead, Mazumdar and others have suggested that other particles the LHC could detect might shed light on inflation. The models they suggest are rooted in the theory of supersymmetry, which connects the two known basic types of particles, the ones that make up matter (fermions) with those that carry the fundamental forces (bosons), predicting that each fermion has a heavier bosonic counterpart and vice versa. The discovery of supersymmetric particles or "sparticles" at the LHC could help solve key mysteries within the Standard Model. For instance, the invisible dark matter thought to make up most of the mass in the universe could be a kind of sparticle known as a neutralino. If the inflaton is also a sparticle, Mazumdar says it must have ended up with a relatively low energy density, one potentially detectable by the LHC; otherwise, the inflaton would have helped generate a lower ratio of normal to dark matter than we see in the universe.
If the LHC does prove supersymmetry correct by finding sparticles, Mazumdar's analysis suggests that the inflaton would be a sparticle with a mass of about 1,000 billion electron volts. In comparison, the LHC is capable of energies of up to 7,000 billion electron volts. In May, Mazumdar's team submitted research on how the LHC might discover the inflaton to the Journal of Cosmology and Astroparticle Physics.
Alternatively, Mazumdar says there are supersymmetry scenarios where the Higgs is the inflaton, either by interacting with sparticles such as the superpartner of the neutrino or by itself, work detailed in 2007 in Physical Review Letters and in 2011 in the Journal of Cosmology and Astroparticle Physics, respectively.
Recent data from the LHC, however, might suggest that many current models of supersymmetry may be wrong, because experiments have not yet uncovered any of the sparticles the models predict.
"Ultimately, if the LHC discovers the Higgs boson and nothing else, for me that would favor a Higgs inflation model; if the LHC discovers supersymmetric particles or any other type of new physics, the model would not be so attractive," Shaposhnikov says. "Hopefully we should learn a little more either way when CERN gives an update on the Higgs search on July 4, and on searches for new physics at the International Conference on High Energy Physics later in July in Australia."