A neutron could be a tiny magnet — the equations allow it. But in reality, it barely shows any magnetic properties. One explanation comes from the Nelson–Barr mechanism: a special field spontaneously breaks the symmetry and hides this effect. The solution has a side effect — domain walls appear, boundaries between regions with different vacua.
The authors found a way to get rid of these walls. They showed that the same field can drive inflation — the rapid expansion of the universe in its first moments. The field's potential looks like a double well with two valleys. Inflation rolls along one of them, and afterward there isn't enough energy to jump to the other. The walls simply don't form.
This field is a real jack-of-all-trades. It solves the strong CP problem, drives inflation, and then transfers energy to ordinary particles. If you add right-handed neutrinos, the field also breaks CP symmetry in the lepton sector, creating a matter–antimatter asymmetry. So one mechanism unifies cosmology and particle physics, eliminating the main difficulty of the original model.
Inflation stretched space faster than light, but this doesn't violate relativity: it was space itself that expanded, not motion within it.
The idea of a field that simultaneously controls symmetries and the expansion of the universe echoes the 'inflaton' from Iain Banks's Culture series.