Supercooled phase transitions in the very early universe

The universe might have had a prolonged exponentially expanding phase caused by its being stuck in a metastable state of the grand unified phase transition. The only way that it could exit from this exponential expansion without introducing too much inhomogeneity or spatial curvature would be through a homogeneous ``bubble'' solution in which quantum tunnelling occured everywhere at the same time. This would produce more baryons than the conventional scenarios.