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Eric Linder’s talk began with the fundamental concept that matter and energy are two forms of the same thing, related by Einstein’s formula e=mc2. Matter and radiation can be created by energy as well as annihilate to create energy. This can be used to describe the early universe, when the universe consisted of lots of energy, matter, and radiation in thermal equilibrium. He then described the various eras in the history of the universe.
The early universe underwent a period of rapid expansion known as inflation at some point between 10-37 seconds and 10-12 seconds. This placed the full universe out of causal contact with the visible universe and wiped out all initial conditions. This memory removal of the early universe is referred to as cosmic amnesia. The energy that was used to drive inflation was converted to matter and radiation at the end this era.
This era of reheating is known as the radiation era. Inflation, similar to other phase transitions, could have left behind many topological defects as evidence. Cosmologists are currently searching for these.
As the universe expanded during this era it also cooled, which resulted in a reduced number of particle interactions. Thus massive particles eventually stopped being created. This era was referred to as "freeze out" and the number of particles became constant from that era on. Eric further explained that from conservation of energy there must have been the same amount of particles and antiparticles created. This gives rise to the major question, “Where is the all the antimatter?”
Eric clarified that the only observed antimatter in the universe has been created synthetically in laboratories. Current observations support that our universe consists of normal matter. Evidence for this has been found from directly probing our solar system and observing gamma ray annihilations on very large scales. Theoretical problems with the current existence of antimatter include problems with charge parity and causal separation after inflation. The Standard Model offers solutions to this problem, but not to the magnitude necessary to completely model baryogenesis. The talk concluded on the mysteries of matter-antimatter asymmetry and other related questions that remain about the universe.
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