| A | B |
|---|
| Cold Dark Matter | Dark matter composed of heavyweight particles that formed during the GUTs or before. |
| Decoupling | The epoch where nuclei and electrons combine to form atoms. |
| Flatness Problem | One of two problems with the standard Big Bang model, which is that there is no natural way to explain why the density of the universe is so close to the critical density. |
| Grand Unified Theories | Also known as the GTU epoch when the strong and weak nuclear forces are unified but gravity has separated out as a force. |
| Horizontal Problem | One of two problems with the standard Big Bang model, which some regions of the universe have very similar properties are too far apart to have exchanged information in the age of the universe. |
| Hot Dark Matter | Dark matter composed of lightweight particles that have masses less than an electron. |
| Inflation | A period of unchecked expansion in the universe after the GUTs epoch. |
| Matter-Dominated | The cosmological terminology that is used to describe the current universe after the crossover point. |
| Pair Production | Early Universe interaction when two protons interact to create a particle – antiparticle. |
| Primordial Nucleosynthesis | The production of element heavier hydrogen shortly after the Big Bang. |
| Radiation-Dominated | The time before the crossover point where there was more radiation than matter in the universe. |
