The Big Bang
Our universe is not the only universe that will ever be. It was created by the Big Bang, a long time ago. Since then it has been expanding and cooling down. In the beginning of its lifetime, objects of matter, like planets, rocks and stars, are abundant. The young universe is compact and warm. The more time passes, the more the universe will expand. This expansion goes hand in hand with a decline in temperature. Black holes grow in their numbers, as well as their size. The balance starts to shift from matter to antimatter as the black holes continue to consume all surrounding matter and convert it into antimatter.
The black holes obtain energy from the matter they consume. This causes the temperature inside the black hole to become increasingly colder, millions of degrees below 0 Kelvin, the absolute zero for matter.
An infinite cycle
This process cannot be stopped. The black holes keep growing, with an increasingly strong field of negative gravitation. Black holes that encounter each other will merge. Eventually, all matter in the universe has turned into antimatter, held in the giant black hole that remains. As there is no surrounding matter left, the black hole's source of energy is now depleted. Its temperature will start to rise. When the temperature reaches 0 Kelvin again, the antimatter of which the giant black hole is made, can no longer sustain. It comes apart in a new Big Bang. A new universe is born, the cycle is completed.