inflation

From the phase transition of the grand unification era the universe moved into a state referred to as a false vacuum. The phase transition was very slow in relation to the speed of cooling, leading to a special state referred to as supercooled. Importantly, symmetry was not broken; supercooling of the universe occurred with the values of the Higgs field remaining at zero. This caused a state of false vacuum. The temperature was decreased and the energy density of the state was concentrated entirely in the Higgs fields. Since the symmetry was unbroken when it would normally be broken, there was a kind of tension in space, a large negative pressure.

Negative pressure has the effect of a gravitational force that is repulsive. This was what drove the rapid expansion. During this period the universe grew by a greater factor than it has in all the time since, increasing in radius by approximately 10³⁰ times.

The most unusual property of the false vacuum is that during inflation, the energy density remains constant. In other words, as space gets bigger, more energy appears! It is in this way that all the matter and energy can be created from virtually nothing.

Once this expansion took place the transition to a broken symmetry phase finally occurred. The energy density of the vacuum was released, rapidly reheating everything back to the "normal" level.

- Jx, Fx (ed)