Postinflationary

Postinflationary refers to the period in the early universe that follows cosmic inflation. Cosmic inflation is a theoretical epoch of extremely rapid, exponential expansion of space that is believed to have occurred immediately after the Big Bang. The inflationary epoch is thought to have lasted for a tiny fraction of a second, from about 10^-36 to 10^-32 seconds after the Big Bang.

Following this period of superluminal expansion, the universe is thought to have entered a phase known as reheating. During reheating, the energy density that drove inflation was converted into a hot, dense soup of fundamental particles and radiation. This marks the beginning of the "postinflationary" era, a period that is characterized by a more conventional expansion and the subsequent evolution of matter and energy as described by standard Big Bang cosmology.

The postinflationary period is where phenomena such as baryogenesis (the creation of a matter-antimatter asymmetry), nucleosynthesis (the formation of light atomic nuclei), and the formation of structures like galaxies and clusters are understood to have occurred. The properties of the universe observed today, such as its large-scale homogeneity and the spectrum of cosmic microwave background anisotropies, are often explained as consequences of the initial conditions set during inflation and the subsequent postinflationary evolution. The study of postinflationary cosmology is crucial for understanding the formation and evolution of the universe from its earliest moments to its present state.