The Defect at the Birth of the Universe

In the Economist:

At the precise moment the universe began, its constituents—which today appear as fundamental forces such as gravity and electromagnetism, and subatomic particles such as electrons and quarks—were unified into a single substance in the extreme heat of the explosion. As the universe expanded, though, it cooled. And as it did so, it went through phase changes, just as steam condenses to liquid water that then forms ice as the temperature falls. At each point at which the phase of the universe changed, one of the forces of nature became distinct, or a type of matter emerged as being different from the others. Only when this process was complete did the familiar pattern that makes up the laws of physics properly emerge.

One theory, devised several years ago, has it that each of these phase transitions is marked by the formation of defects. Such imperfections are analogous to the misalignments between ice crystals that often form when water freezes. These can be seen both in ice cubes and on frost-covered windowpanes in the places where growing crystals have met. Cosmic-defect theory, as it is known, holds that a similar process would have happened as the newborn universe cooled.